One thing worth mentioning.. I've already seen a couple of people throwing up "placeholder" threads in the sub-forum. This is only going to clutter up the sub-forum, I'd suggest that the only threads allowed should be lowballs which are currently ongoing, about to begin, or have recently ended. A ton of "reserving my spot for a lowball!" or "thinking about having a lowball!" threads are just going to muck things up and make it more difficult for buyers to locate lowballs they might actually be interested in.
I wouldn't imagine placeholders to be an issue as long as the subforum is sorting with most recent updates first as usual. The non-active lowballs will be pushed down fairly quickly and only move up once the preview is up and/or the lowball has begun.
I'll agree with pretty much everything Shrike has had to say.
I'm sure we can all agree that there is never really a lull in lowballs anymore, so finding a time when everyone would be happy with a move was probably impossible.
Finally, as for the worries about people not seeing them or being able to find them, I honestly don't think it will be an issue. Have you ever known a CAG not to seek out something at a good price?
They'll find the subforum, don't worry!