Blizzard sort of already did that, starting in Wrath of the Lich King.
As I’ve said, when you say that a group or faction doesn’t exist, you have to make the world reflect that. In WoW’s case, if Blizzard had cared about being consistent and dissuade requests for high elves, the Silver Covenant would have never been created. The ranged lodges in Cataclysm would house every other race but high elves. The Kirin Tor Offensive would have no high elves, and Varessa Windrunner would have been made into or introduced as a Blood Elf. That’s how you remain consistent with the small regiment claim.