All the Idea's sound good, but I would suggest a:
General Modeling forum (newbies introduce themselves, people show off their latest build, in progress...ect).
A Painting forum (for questions about painting, polishing, waxing...ect)
A trade or buying forum (ask about good deals or not, make trades with people, or buy off people)
And a lost part forum (for people who need parts that have been lost, or just need the parts for Customisation)
Just my .02 cents.