I think a free wiki might be the best way to go - getting money involved would give wankers legitimacy when they whined about people writing articles with biases, or whatever. I don't think an LJ comm is really needed, and might actually detract from the wiki itself - maybe you could make a central post for planning and just link it back on various comms?

The only toes I'd worry about are Fanhistory.com toes, and those...are not well-balanced toes. Put mildly.

Since it's your idea, I'd say you could choose mods as you saw fit.