Add a new up/down (like it/don't like it) thread rating system.
Admins choose between the current 5-star thread rating system and the new one.
Rating a thread affects the thread starter's total reputation score (positively or negatively)
Overhaul the reputation system so it's more of a post rating system:
Add a new up/down (like it/don't like it) post rating system.
Admins choose between the current reputation system (with rep comments) and the new one (no comments, just up/down arrows/thumbs).
Post rating score would be shown in the postbit
Posts would be collapsed (but viewable) if below the admin-set minimum threshold (-5, for example).
Users can set their own custom minimum score and posts below that score are collapsed by default.
Have a new button when viewing a thread that allows you to sort the posts by their rating/score instead of having them in chronological order. (except the first post would stay at the beginning)
Add a forum setting so threads in that forum are automatically sorted by post score instead of chronologically.
These changes would go a long way towards helping vBulletin be more suitable to a question/answer format rather than conversations. It would also make vBulletin more user-moderated; if a majority doesn't like a post, it can be automatically hidden, if the admin sets it up like that.