Can I advocate for the free safeguard every few levels to come back? Maybe it can be a feature you unlock after getting the achievement where you beat a pack without using safeguards, but for packs that have 20+ levels and difficulties that bounce around a bit (Crazy Party, Vocalloid), those few free safeguards gave you the chance to get through. I can understand you don't want the game to be too easy, but if we earned the privilege, like with the save setting, you could consider letting us have that back? The same with insurance. The current save setting isn't really worth using if failing means you lose your save. I know what you're trying to do, but there can be a fair middleground, can't there? Say, you buy an insurance, and those beatcoins aren't coming back. If you buy safeguards after getting the insurance, or change packs, you lose your save, but you get to try from that point every time until you beat the pack. There's challenging and there's I-will-go-insane-if-I-have-to-play-through-all-these-damn-slow-levels-one-more-time.
Also, being able to adjust the volume of the tracks would be nice, or have it so by default, the prompts are louder than the music by enough that you can hear them over it. The DBZ pack is a prime example for why something has to be done about this issue.
You can take my feedback or leave it, but I'd ask that you at least consider my suggestions for the reasons outlined above.