Maybe people who want to do an AMA can put forward their name, and each week 4 or 5 people would be given the opportunity to post one. Could be randomly selected, or have a waiting list, or some combination.
That's a very good idea.
agreed
edit-maybe limit it to, say, 2 at a time on the front page? Minimum, in case an older one got resurrected for whatever reason. Some kind of "cop" in charge of them so noobs with 700 posts aren't getting in ahead of an old timer (by forum standards). Maybe the cop even starts each one?