There are lots of post-by-play forums that span genres, universes, fanfic-doms and such already.
Personally I prefer roleplaying communities where there are a variety of worlds to play within at any given time. I mean, some days you wanna be a dragon, other days you wanna be a spaceship pilot, other days you wanna be a tribal warrior, right? And some people like a more cheerful world, while others like a more gritty one.
I think my desire is to weave one tale with many stories centered in it. To make real world that can stand up on its own, alongside other players and writers. I have different things I want to do on a day by day basis as well, but (to me) that is what my bookmark bar is for
You might look at it from the perspective of a team of writers as used in television shows etc. An overarching set of guidelines for development are established and then individual episodes are farmed out to individual writers (or smaller teams within the larger team) to bring out about the required guideline's immediate needs as well as create their own story within that "universe".
That strikes a chord with the feeling I get when I think about this project ^^ Perhaps it's just a matter of finding the right writers.