Taking this a step further (not making any promises yet  :D  )... I'm thinking this would take place on an Earth where super powers are a very recent phenomenon (< 6 months), and super beings are rare (but becoming more common).  No mutants, no aliens, no ancient mythological beings.  Essentially, one day you were J.Q. Public.  The next, you could fly, or lift a boxcar, or mind-control dogs or whatever.  As they always seem to, circumstances would draw the team together, probably by way of me giving each player a writing prompt to write themselves into the beginning of the first episode.

Character generation: I have a modified version of the V&V tables, and I'd have players taking turns posting dice rolls to determine powers (and a weakness).  this way, players can suggest ideas to tie disparate power elements together (plus its fun to see what other players get!).  Players would make 5 rolls (plus one weakness roll), dropping one at the end of the process.  The weakness that is rolled can be removed at the cost of dropping another power.  Once all the rolls are made, I'd likely allow each player to pick a power to complete their concept.

Does that tickle fancies?  Or cause fancies to cease smiling?  :D