Have a look at
http://www.talkaudio.co.uk/index.php/index.html - these guy used to run vb3 like this site does but moved to ipboards (I've been a member there for the last 10 years). Topic is car audio but I think functionally covers in interesting array of elements such as news, forum, classified, gallery etc that makes for a structural model worth considering.
Classifieds could be useful but brings it's own pitfalls dealing with spam/sellers/complaint etc. TA used to have free classifieds but you needed to be a member to 30 days and have 50 posts. Now its a small fee per advert or you can pay an amount per year which also gives you assess to a paid members forum section with offers related to a company with close links to the forum. The more positive side of the classified / paid member is that the forum can be come financially self sustaining.
The news section facelifted with more functionality such as comments or social sharing could be useful.
Event lists would be really use and a dedicated gallery with user uploads.
User blogs could be useful for people who want to create a build log but don't want to use the forum format or a blogging service.
A video gallery could be quite nice which gathers together grouped kit car videos, technical videos etc.
A technical forum subsection might be quite good to gather together general tech threads that might be useful for all kinds of kits.