Here's my suggestions:
* Multi-choice signatures (up to 3)
* Multi-nickname choice (1 username as login name only, but use 3 selectable nickname for displaying in the post)
* The registered user can decide to post anonymousely by selecting one of his nickname and did not allow the others querying their profiles.
* Switches to grant groups/users/boards/categories privileges.
* Forum boards can be applied as an article/news/download center, etc.
* More features for users & sub-communities, such as calendar, event manager, voting center, board master's page/news/notes.. blah, blah, etc.