From what I've read To on powers are tabled as they should be because the only times they're fun or not OP is in card games like Munchkin or in the actual game Toon.

I can see the game being handled light heartedly but agree that not everyone is good at telling jokes or coming up with amusing situations.

So turning my Muse on the subject I propose the consideration of several focus points.

1: (here's the one that's most likely to draw complaint) Killing is not an acceptable action. I say this because unless your sense of humor is geared towards the macabre it's just not funny or fun.

2: The world could be and odd world were all of humanity have some from of ability but usually low level like the Side Kicks in Sky High The movie such as being able to glow or change color.
People on this world could be ranked in power level from puberty and those of the higher levels dream of becoming established heros just like kids dream of turtning pro in a sport.

3: If two was appealing and people desire a school setting then we could say the Heros are actually attending a kind of Trade School to become a City protector. Going to trade school as opposed to attending required school would limit the reach of school authorities.

Just letting the imagination run free here