Hmmmm. One approach could be a standard wiki bridge between vbulletin and mediawiki. One such bridge is available (and properly supported) over at
nuHIT.com - vbWiki Pro Features . Hell knows I'd have no time to support a massive project like setting up a new wiki, but then again I might not have to - wiki's are community led anyway, and all it needs is a design schema and a few dedicated people to keep revising it.
Sound like a plausible idea?