“X who do Y” may be something the players decide in Session 0, but it really does need to be decided. I have enough trouble getting sessions up and running when they have a clear goal; I can’t imagine how utterly chaotic and tangential things would get if the players had to figure out what their characters were doing.
Bill, depending on what about Wraith superheroes tickles your fancy, Greg Stolze’s Better Angels might do the trick. The conceit is that supervillains are actually demon-possessed mortals, and the demons are run by another player much like the Shadows in Wraith. It’s got some very hippie-indie-game mechanics, though, like your stats being based on moral approaches and also acting as your damage tracks. Plus it’s One Roll Engine, which might be a selling point or might be a warning flag.