This is one of those things that should probably be made a new feature on the forum, the ability to switch back and forth between moderated/unmoderated threads. It would probably piss a lot of people off if members started switching normal threads to self-moderated ones and deleted all the posts
I hope that will never happen! I don't want random users to have delete-access on any post I ever made in their topic. It would also greatly benefit scammers.
I think it is reason on which theymos decided to not allow the switch from non-self-moderated topics to self-moderated topics. I saw projects that have non-self-moderated topics that try to lock them and created a new one, self-moderated of course.
Despite of the restriction to prevent any abuse from scammers, I think the opposite conversion is good: self-moderated topics to non-sel-moderated topics. I don't see people have bad intention when they do such conversion.
As discussed above, there is method to do such conversion unofficially but if possible, it's better if the forum allows to do it officially, without step to move topics back and forth between boards.