I'm not going to profess to know the first thing about game development or zone design.
Would FunCom ever consider making developer kits available for users to try and create new content? This content (zones, pvp maps, and/or quests) would have to go back to funcom for final approval, editing, and rewards before being posted but it might provide a little more content with less developer hours.
The review of work is critical to avoid the unmitigated disaster user created stuff that populated a lot of Neverwinter's foundry.
Users that submit content that gets incorporated could be given funcom points or extra time on their subscriptions.
(By the way this isn't intended as complaining about a lack of new content but a way of hopefully seeing more).