When I say that I have previous experience, I'm referring to the creation of a combat model. I did not code it, not at all; I knew a bit of how it might work, but I don't know programming near well enough to be anything close to useful, except to generally be aware of what does and does not work.
My browser-based game Tarranoth, which has sadly gone to that great database in the sky, would've been a really good way to show what I'm capable of, numerically. Suffice it to say that I got a lot of firsthand experience working directly with a coder.
If you work with me, you'll be working with someone who doesn't code but who does generally understand the limitations this medium presents. You'll also be working with a team player who's open to ideas, and a person whose work ethic is top-notch. I won't give you shoddy material to work with. I won't make up bogus mechanics for one function that only ever gets used once or twice. I'm in this to create a good solid RPG that players will like, and which will offer unique challenges. When I brainstorm, I don't just go "You know what would be cool?" and then expect someone else to go through the scrap pile to salvage the bits that will work and the bits that won't.

To answer your question about platforms, I personally am familiar only with Windows, but cross-platform support would be lovely. I do intend that this be a PC game, not an IOS game, however. I'm okay with mac support if that's possible, but I don't wish to create a genuine IOS project here.
Regarding tools...I'm not sure here. BGT was used for Paladin of the Sky and it looked pretty solid, but if something else (or combinations thereof) could provide equal or better experience, I'd be happy with those.

At least to start with, it is probably best that the game use SAPI or some kind of synthetic speech. I can worry about voice-acting when, and if, this takes off. I'm not talking about a two-dungeon audio game though...this would be the sort of thing that might take players a good twenty hours to finish, and that's if they know what they're doing.

If you have further questions or comments, I welcome them.

Paladin of the Sky is maybe ten to twelve hours if you know what you're doing, twenty to thirty if you don't. Some neat mechanics, a sometimes infuriating magic system, lots of maps to run around on.
It takes place largely on a ship, and I want to avoid that. I want you to run around in a whole world. Multiple towns, maybe a couple of slightly larger cities. Roads through hillsides. Caves. Maybe a desert. And some good old-fashioned dungeon-ish type stuff.

Here are the things I know I'm after, regarding some combat nuts and bolts.

- per-round fighting; that is, no timed stuff, no active time gauge...you can take all the time you need to strategize
- four elements (earth, water, air and fire); you get four characters in total, and each character gets one sphere of magic...your choice
- skills and spells unlocked by level, and enemies that give experience when killed
- optional secret skills/spells, perhaps one each per character, which have to be quested for
- enemies can have elemental resistances and immunities, and can sometimes heal if you hit them with an inappropriate element
- save points, not a save-anywhere feature; I want the game to be a challenge, an if you can simply save after every battle, you take some of the difficulty out of it
- status effects (blindness will lower physical accuracy, muddle will make your magic very inaccurate, silence will render you unable to use magic, paralysis will render you unable to use physical attacks, sleep will make you helpless unless you are hit)
- bosses with attack patterns (performs attack a, then attack b, then attack c; will respon with attack d at any time when condition x is met) ..and more, obviously

As far as ideas for a raw story, I don't have tons yet. I know that I want four characters you can play, hopefully in a party all at once (like Entombed). I know that one female's name is Jann, and I think your non-main character's name (the male I mean) is Breck. Sue me, I like slightly odd names.
The idea, as it stands, is a bit simplistic, but I'm open for suggestions on this. It's an average day in the life of your main character, but one evening after wandering the countryside hunting or something, he returns home after seeing some strange lights near the village and nearly everyone is acting strangely. There's a smoking hall where the village green used to be, and a bunch of chunks of rock around its edge. The townspeople seem enthralled by the fragments, and when the main character gets close, he gets a sort of vision...someone tells him to go no closer, lest he be corrupted. At that moment he notices that some of his former friends and loved ones are looking his way with some hostility in their eyes. He takes off, and isn't followed.
This is probably the prologue of the game, and you get dumped into the action trying to find someone sane who can explain what happened.
I am not planning for an epic good guy vs. bad guy thing right from point 1. I dislike evil purely for evil's sake; my villain may be a villain, but there's going to be method to their madness.
The game is essentially going to be the main character's journey to unravel what's going ion, and to discover the identity and objective of a group of three hooded figures who are always nearby when calamity strikes or when things become strange. Someone has, without quite realizing it, stumbled on something both wonderful and terrible, and they'll do almost anything to protect it.

Hate to be a back seat moderator, but this goes in development room.

It doesn't have to be ready right away. If I know I've got people interested, I can work out a script and maybe try and get one person to make me a battle engine so I can test stuff for balance. Failing that, I also want to make some more immersive details (such as knowing what people and items look like). A lot of work, overall, and most of it text-based so all a coder would have to do is put the right text in the right place.

My basic idea for mapping is grid-based, at least roughly speaking. Having something similar to the tone system in Paladin of the Sky would be good, but when I say grid system I mean that hitting left arrow would move you to the left, not turn you. I do plan for some mazes and a few puzzles, but I don't intend this game to have insane platforming angles.
I dearly want the game to have a full party though...as in, it's not 1 vs. 1, it's ultimately 4 vs. however many enemies there are. I don't know how tricky this will be to code. In the party menu (maybe accessed by pressing p) you could see your character's stats, experience, skills/spells and status. I would want to use something like the e or x key on maps to examine something you've bumped into, whether it's a chest or a person. Barriers could yield descriptions too...in a town it might just be a wall made from red bricks of clay, in a forest it might be a deadfall.
I would like also to add, at some point in the story, a crucible of synthesis...an item you can get, optionally, where you put two or more items in it, walk around awhile (or fulfill some other requirement) and then the crucible opens to reveal a new item.

Short answer: no, this doesn't have to be done right away.

Here's an overview of what I'm after for a basic combat engine, as far as specs go. Tell me, if one or more of you could, if this makes sense and/or would be too hard to code. I should think not, but I'm not a programmer either.

Statistics

Each entity capable of combat will have various statistics which govern how well they can perform. Below, I will discuss each.

HP: hit points. If this drops to 0, the entity is incapacitated and unable to battle unless revived by an ally.

MP: mana points. This governs the use of magical spells. If MP reaches 0, all skills which would consume MP are no longer available. MP can be healed in or out of battle using items if necessary.

Stamina: This is a gauge of your ability to perform actions. Characters begin a fight with 25 stamina (this can be enhanced with equipment or augmentation, see far below). Regular attacks use up 2 stamina, using an item (on you or on someone else) uses 1. Defending uses up 2 stamina as well. The Wait command will leave the waiting character completely helpless but restores 5 stamina. Stamina naturally recovers at a rate of 1 every round, and there are somewhat rare items which can be used to refill stamina, though it should be noted that many of these may damage the user's HP or MP as payment. Magic does not require stamina, because it requires MP, but physical skills can have costs anywhere from 3 to 12 stamina depending on their power and usefulness. Management of stamina will be an integral part of battle strategy.

Accuracy and Agility
These stats determine how often hits land and how often hits are dodged. If your accuracy and an enemy's agility are equal, the chance of a hit is 75 percent. For every point of difference either way, the percentage goes up or down by 1, to a minimum of 10% and a maximum of 95%. For instance, if you have 10 accuracy and your opponent has 8 agility, you have a 77 percent chance to hit them. If they have 100 agility, you only have a 10% chance to hit them.
Note: Accuracy and agility figure into physical attacks only. Some physical skills have agility and/or accuracy modifiers when used, such that a particularly wild attack might be less accurate, or a low-damage attack might be particularly so. Some skills will grant the user extra agility, followed on the round after by an attack which would then remove the agility bonus.

Focus and Foresight
Focus is the accuracy of your magic, and foresight is one's ability to dodge magic. Owing to the more costly aspect of magic, the base chance to hit is 85 percent instead of 75 percent, and it takes 3 points to change the percentage by 1 either way. For instance, if your focus is 100 and your enemy's foresight is 79, you have a 92% chance to hit. Unlike melee, magic may reach a maximum of 100 percent (which would take a minimum of 45 points of difference between your focus and your enemy's lower foresight). Also different from melee, magic's base chance to hit can never drop below 30%.

Damage and Armour

Damage, in this case, refers to how much pain you dish out with physical attacks. Damage is a fixed number, and equipping a weapon directly modifies it. For instance, a character whose damage is 14 who equips a sword whose damage is 4-6 now has a damage potential of 18-20.
Characters will gain bonuses to their damage as they level, or by using certain items.
Damage compares directly to armour to determine how much an enemy is hurt. The overall damage number is calculated first, then it is compared to the enemy's armour number. If the damage number is higher, the difference is dealt to the enemy as HP loss.
Example: damage of 20-23, armour of 6-6. Damage will be 14-17 (rolled randomly).
Armour is another fairly innate stat which can be enhanced by certain items and/or events. It will probably never become as godly as damage, and some characters are naturally more armoured than others. Wearing armour which has an armour rating naturally boosts this stat further.

Slash, Bash and Thrust
Weapons do different types of damage, and naturally, certain monsters are more resistant to certain types of attack...or weak to them, as may be the case. It may not be wise to use a sword on a stone golem, but using a hammer might work well, for instance.
Certain weapons will add a damage modifier while equipped, such as Bash+4. This means that any attack which uses the bash damage type would have 4 automatically added to its damage before calculating how badly the enemy will be hurt. It also means that attacks of a differing damage type will be unavailable. No using Tendon Slice while wielding a hammer. Certain armour will have modifiers against certain types of damage as well. A crystal breastplate might, for instance, have thrust+3 and bash -5, which means that it will help you resist thrusting attacks but will lower your armour against bashing attacks by 5.
Note: these single numbers will modify both sides of a spread...so if a spread is 3-5 and the modifier is +4, then the spread is now 7-9.

Examples
Jann uses a glittering rapier with a damage rating of 8-12 (thrust+6) to attack a stone golem (bash-5, thrust+7).
Jan's natural damage is 7. The golem's natural armour is 11.
Jann's damage is: 7+(rand 8-12)+6 = thrust damage of 21-25
Golem's armour is: 11+7 = 18
Thus, you would roll a number between 21 and 25, then remove 18 from that number, and that's how much the golem is hurt for.
Please note: certain characters can and will get bonuses to specific damage types as they level, so it will not be quite so easy to simply switch all characters to using a weapon of a certain type. This may help, but it will not be so crushingly advantageous as it might appear.

Magic Attack and Magic Defense

For want of better terms, these determine how much oomph your spells pack, and how well you can survive when hit with spells.
This is handled in much the same way as damage and armour. Certain pieces of equipment will augment your magic damage, and certain heavier pieces of armour, for instance, may impede it. Nonelemental magic is rare, however, and thus, most magic will be of an elemental type.

Earth, Water, Air and Fire

Much like slash, bash and thrust, these are specifics of magic damage. If you are using a Fireball spell, its damage will obviously be fire. Your magic damage will be calculated by taking your natural magical attack, then adding the spell damage on top of it, then factoring in the enemy's resistance to (or weakness to) that elemental type.
Many enemies will have no elemental affinity to worry about, but some certainly will. Observe an example:
Breck uses Chill Cascade (+12-18 water) on a Lava Beast (fire+9999, water -20).
Breck's magic attack is 13, and the Lava beast's magic defense is 9
Breck's overall damage with the spell in question is:
13+(rand 12-18) = 25-31
Lava Beast's overall magic defense is 9+(-20) = -11 (he will take 11 more damage since this is a water spell
Thus, the damage he will take from this spell is 36-42 because he is weak to water
See how this beast had 9999 fire defense? You will categorically never be able to have such high numbers without cheating, so you will not be able to hurt the beast with fire.

Each player in your party will choose one sphere of magic. Once that sphere is chosen, it will be unavailable to the other party members. As such, once a sphere of magic is chosen, the player will slowly gain innate damage boosts when using that element.

Speed

This stat has no other function except to determine who strikes first on any given combat round. It is a fixed number to begin with, but which will slowly go up as characters level. Some equipment can greatly raise one's speed, but usually at the cost of providing little in the way of protection or other benefits.
A quick note about speed: as you become wounded, your speed drops. For every 10% below your max HP you fall, your speed will correspondingly drop. Barring other skills which may override this mechanic, this will mean that having a party at fairly low health is a really excellent way to get it killed by a large group of enemies.

A few finishing notes, for now

1. If the accuracy/agility or focus/foresight check yields a miss, the game does not need to calculate any further. A miss is a wasted attack and yields no damage, generating only a miss message.
2. Damage or magic damage that is lower than armour or magic defense yields a result of 0. The game will generate a message such as "Jann attacks the Stone Golem with her shimmering rapier, but the foe shrugged off the blow", or "Breck uses Lavastorm on the Lava Beast, but it seems unaffected".
3. If there are enemies or bosses who possess attacks which can be cancelled by successfully attacking them while they charge, damage must be dealt in order for the interrupt to succeed. Attacking something for 0 damage will not sufficiently break its concentration.
4. If a weapon possesses a modifier to a damage type, it goes without saying that the damage type it will inflict will match. If a fire rod gives you a +3 to fire and a +1 to bash, then you apply both. If a Soulrender gives you +20 to slash, then it will be a slashing weapon.
5. Some enemies, or rare pieces of equipment, may possess a trait known as "eater" or "absorb". This will only be true for magical elements, and not physical damage types. In such a case, using an element on an affected entity will cause whatever the damage would otherwise have been to be added to the target's HP total instead of removing it. In this way, it is not possible to give an enemy more than its max HP, but obviously, attacking something that absorbs your element of choice probably isn't going to work well.
6. When a weapon possesses a magical element (and it will happen, albeit not too often), calculating how much damage is done becomes more complicated:
a) If a skill is being used, and the skill has a damage type ascribed to it, then that damage bonus is also applied
B) In a case such as this, all bonuses are figured in, and all resistances or weaknesses of the enemy are also figured in.

Observe:
Jayde is wielding a Lightbringer (5-10 damage, fire+4, slash+7) sword.
Jayde's damage is 14, and her innate slash proficiency is 3. Her innate fire proficiency is only 2.
She wants to use a skill called Tendon Slice. This skill does 13-17 slash damage.
So here's how you calculate how much she's going to hurt her foe for:
Slash damage = 14+3+7+(rand 5-10)+(rand 13-17) = 41-50
Fire damage = 4+2 = 6
Total damage = 47-56
This is the damage she would do against an enemy not resistant or weak to slashing attacks, and not resistant or weak to fire attacks.
In order to deal with a case where resistance or weakness would factor in, the calculations for armour and magic defense are done in that order.
In text, player-side, you might see something like:
Jayde uses Tendon Slice on the angry goblin, dealing 27 damage
The flames on Jayde's Lightbringer deal an additional 3 damage
This way, if a monster is weak to slashing attacks but happens to absorb fire, you will hit it hard with the physical part of the attack but will heal it with the fire you wield.
...Complicated, I know, but there it is.
One last note on this subject, but magic spells will probably never use slash, bash or thrust damage types. I suppose I could do that, but it seems like a lot more work. In that instance, however, the magical part of the damage would be calculated first, and the slash/bash/thrust stuff would be an after-effect. The difference here is that you don't need a weapon to cast magic, but you will need a weapon for many of these skills. Magic, lacking a specific instrument, will probably not be stuck delivering random slash/bash/thrust damage because of the weapon the magic user is holding.

Thanks for reading. Do tell me your thoughts.

At a first glance this seems reasonable and robust enough. It is relatively easy to code, too.
Rob

I'm going to include some boss ideas and a couple of skills/spells with some more complex stuff behind them, I think, see what you guys think of those, too. I'm glad nothing so far immediately strikes you as overly difficult. Thanks for all the feedback, by the way.

A few things:

1. I am not against something being screenreader-based. Voice-acting is secondary to me. If I can get voice-acting, great. If I can't, oh well.
2. I am absolutely dead set on a turn-based RPG where battles are random, aka Final Fantasy. Perhaps for some optional bosses you will be able to approach them and be able to see that they're there, but generally I want it so that, barring fixed fights, you do not know what sort of encounter you'll get next, or exactly when. Some areas (outworld, dungeon, etc), will have random enemies. Some areas (cities, towns and houses) will be safe. Certain maps will have certain encounters (you won't get a wicked strong dragon rampaging around the first area of the game). This turn-based thing is one issue I really, really don't intend to change my mind about.
3. Regarding a gamebook sort of thing...to some extent I want there to be choice, but I don't want the game to play like a gamebook. There may be things you can do to make certain people like or not like you so much, and I fully intend for a few subquests to have mutually exclusive choices.
4. The way my story is shaping up, being "evil", as such, would consist of just letting the villains continue to do what they're doing. There's really no game there. I understand what you're saying about good and evil, and perhaps there will be a few different endings with various degrees of quote-unquote good, but I feel like the more open you make a game, the more you make it like a sandbox. I'm not a total purist, but I do like a bit of honest-to-goodness driving force in an RPG; if you constantly let a player choose to be good or evil, it results in two soft options, while making them commit, to some degree at least, to the side of good means that you can focus a great deal on one side of the spectrum.
5. That said, a few things from the villain's perspective are par for the course. The player is going to know and learn things that the protagonists themselves, in-character, maybe don't know, or don't know until much later at any rate. Probably the villain stuff will be cutscene-ish, but it'll be there.

I want to go beyond the check-box sort of deal.

Let's say that you're in a tower, and on the third floor you come across a locked door. You obtain the key, unlock the door and, lo and behold, there's a prisoner. Simply by going out of your way to have unlocked his room will be enough to get you whatever that particular side-quest entailed. If you did the dungeon without rescuing the prisoner and never came back, then let's say his wife, who's back in town, will always pine for him and will never help you (whereas releasing him causes her to react more favourably toward you).
I do like that actions might sometimes change how people deal with you but I want to stay away from check boxes or simple radio buttons to select. I like the player having to go find stuff, or bring things to the right person, rather than just clicking a box after a "Will you rescue or kill the princess?" prompt.

I am thinking that there are three villains, really. The main one starts out being angry and frightened, and by the end has simply become desperate to keep what he has at all costs. Not evil, per se, but letting him have his way is going to hurt a whole lot of people. The second villain is related to the first, and knows in her heart that what's going on is wrong, but can't find it in herself to take the right side. The third starts out quiet and fairly unknown, just helping the antagonist's cause, and then I think something's going to happen that sends this last villain rogue in a big way.

Hello Jayde.
Well any of these could be added easily. I'm not sure how you would get the game to follow along with your computer's clock but it is definitly easy to have a timer so that at a certain point in the game it turns from day to night. I really like your idea since it would mean that you can only do certain things at certain times like go to stores or talk to other characters. Also the idea of different monsters coming out at night is awesome. Maybe you have vampires, werewolves, and others come out at night but they run and hide during the day. Also it would be cool to have weather changes in the game. So if the sun is out and it's really hot maybe your characters get tired quiclly while fighting enemies in the hot son. Or if it's snowing maybe your characters have a harder time fighting because of slipping and sliding in the snow.
And it's no problem at all to add resurrection items you just subtract the value of what the character's stats were before they died. The only problem is let's say you have a wizard and his group to fight. You kill 2 enemies and then the wizard resurrects them. This would make the game overly hard. I think we should add a limit on how many times you can resurrect a character. Maybe once or twice just to make the game fair. Also having a slot for personal items would be awesome. Like maybe you have a necklace that you took from an enemy. Maybe you can't use it as a weapon but you can open your personal slot and have the game tell you when and where you got it.
Also having different slots for body parts is a great idea. You could start wearing things like helmets, boots, pants, armor, to protect yourself from enemy attacks. I think it would also help to have an organization system especially when you pick up a lot of stuff. Maybe you open your inventory and press o to organize your items into columns so you can look for something in particular like a certain weapon or potion.