Hm.. Let me see if I can explain this better.. because I think we're on the same page but I'm not totally sure.

Users 3-400 have been deleted, as an example. We want someone else to be able to sign up and re-write the User 3 id space. #3, 3.jpg/3.png in the avatar database, etc. Is that what deleting everyone but the admin and resetting the auto-increment field would do?

We're not as worried about posts {we've archived everything in another spot} as we are about not having to totally redo the board.