For almost 8 months I'm using this custom mod on vB 3.8 wroted by russian support team and it's amaizing how useful it is. When user want to go off topic while posting he just need to choose an option what time he wants the post to exist. After that time it deleted atomatically and moderators have much less work to do.
If somebody will decide to do something like this I'd also suggest to think about combinig it with doublepost prevention system and post hard delete function.
If anybody like to see how it works on vB 3.8 please pm me.