So, what version of Classic are we going with here? Release day, 1.0? A couple patches in? Classic as it was just before the release of Burning Crusade? There were a LOT of changes made during the course of vanilla WoW, so what is the point at which vanilla servers will decide, "there, that's as far as we will have things advance." I just don't get the logistics of it. What happens when players want a TBC-limited server? WotLK?
I also don't understand where and how it will work. Will mounts not found in Classic be usable in Classic servers? Will Achievements be a thing? Basic UI improvements? The announcement of Classic servers is a can of worms, IMO, because no matter how they implement it, people will bitch and not be happy.