I'm agreeing with some others. Stats always complicate things a bit too much. If you really want to limit us/have a concrete idea of the level of power the heroes possess you could include a section of the character sheet called "feats" that lets us describe the greatest achievement we've made with our quirks. 

For example, someone with a quirk like uraraka would list the heaviest thing she floated (before puking, that is.) but that's just my two cents. I haven't even thought of a quirk yet so what do I know.