Custom sounds: Yes, please add them as soon as possible, the game doesn't come with a lot of them by default like the original sbyw did, so it makes it more annoying to reuse the sounds over and over and over.
Locking maps: Right now you can travel to any map in your maps folder, would it be possible to lock a user out of a map? sort of like adventure at c, you saw the stages, but the creators could set the locked flag, so even if you did see the files, you couldn't enter them.
Shortening sounds: I believe the carpet footstep is a bit too long, hence it not looping properly. That might be because of the file itself, though.
Locking doors: Remember 2DP? You could spawn keys in there, well, a key, and it will allow you to force the user to look for it before preceeding to the nextr room. I want that, but on a bigger scale. i.e, spawning 10 keys that lead to 10 different doors.
beacons: Your choice, either one would work fine. I believe just the tracking in general would be easier to implement, though, again, I want for the builder to set the limit on what you can track.
to number 9 in post 47: I meant make it so we could play a single sound when a player steps on a certain square. Kind of like the events in 2DP, where you could play a sound and make it do something, or you could play a sound and make it do nothing, leaving the player to scratch their head and wonder what was that for.