If you are not sure what to do, I'll suggest to go to a pure genre with some cloned base mechanics until you get a working system, then if you want to start over with a romantic visual novel with fighting scenes with mechas in space, will be easier to set up.
Define approximately the genre (if will be Smash, Tekken, Street Fighter, Touhou, etc.), create the base mechanics, build some prototype in base of that.
When you have that, the health system may appear as part of the testing process, then add the other features you think are needed (special powers, etc.).