I'm gonna make some suggestions about the core mechanics now.
Time stop is done just the way I would want. But we should be able to cancel the time stop without having to wait the bar to fully go down. I mean, Dio and Jotaro can cancel time stop, too.
Time stop is way too spammable. If you have a plan like adding "classes" to game in future, it would be perfectly set for Time Stopping Class . But if you are not planning to add any different skillsets or classes, then you should make it harder to stop time, since it is really powerful. Although, you shouldn't make it too weak either if you aren't going to add classes. Most of the games have some mechanics like Time Slow. People really like it too. But I personally would pick Time Stop over Time Slow, because most of the games don't have such a mechanic and it is just much much cooler and more enjoyable.
I don't know if you are aware of the fact that you can double jump cheese literally ever wall. You probably are aware, though. I mean, you probably tried it but said "Meh, not a big problem. I will fix that in the future." If you weren't aware though, you should make it much harder to climb walls using that trick (if you aren't going to add climbing mechanics to game)
It's really hard for me to do further suggestions, since there is no way I could know what you're planning to add into the game. But I hope I was able to be helpful. I will follow this game's development with huge enthusiasm.