Yeah, you'd almost want all of the stuff I described to happen first and then the result turns into an AMA with preloaded comments for people to respond to.

Undisciplined

Seems like a great start. Here is where maybe a new post type could come into play. While posting, the moderator tags a limited amount of people that can reply directly to the post, while everyone else can reply, just only within those replies.

 This way, the discussion questions never get buried, and the post kinda self organizes.

OneOneSeven

Debates on SN 

I like the idea. My first pass at structure would be
* The moderator creates the post and introduces the topic and debaters.
* Each debater leaves an opening statement in the comments.
* They each get to reply to the other's statement.
* They each pose a question to the other in new comments.
* The moderator poses a question to each debater in new comments.
* The debaters leave a closing statement in new comments.