It's time for Blizzard to get into a more customized race-selection - the players have wanted it for years, since competitors have shown whats possible.
I know lore and reason is a big deal for Blizzard, but deep down I feel it's a matter of engine restrictions/transmogs/additional work rather than for the sake of a story.
Every expac gives us new races from a foreign place, so I don't see why we can't get invaded by friendly gooey blobs called Ditto, from outer space.
Or is there some kind of rule that only races from the Warcraft series of games can be represented? (In that case, give me a Kel'Thuzad model!)