My vote is for the MediaWiki option. I think that making the wiki a separate resource would work better (hazzardnet.com/wiki or similar). If you can't make the single sign-on work, we can always use the same username and password that we have on the forum.
Personally, I'm not that bothered if it looks like the rest of the site - most wiki-style sites I read just look like Wikipedia, but HazzardNet customizations are very welcome.
It would probably be best to initially restrict editing access to Veterans, at least until the templates and main pages are in place. After that, it could be opened up.
We'll have to discuss the rough form of the pages when the great opening gets nearer. For the episode pages, I'd suggest: Brief plot (a couple of lines), Detailed plot (a couple of paragraphs), Cast/Crew, Trivia, Goofs, Quotes and Locations. Did I miss anything? We can have a page for each actor and character that requires one, and pages for important places like the Boar's Nest, Duke Farm etc.