So it's an NPC. But is it a named NPC? Do we get to pick? Would the sex of the NPC match our own sexual preference? Or is it just a random rando from the pool of random? My reaction might change depending on who I wake up married to:
IE: If I wake up and see Anduin Wrynn, I'd immediately kill him and bring his corpse to the warchief. If I woke up and saw Tess Greymane I'd just shrug, accept it, and go back to sleep. If they aren't named and are just some NPC of that faction; it would depend on the race, but since I'm Horde, my chances are pretty good that I won't hate it too much.
Poor alliance though, you could possibly wake up next to a troll (who get turned on by BO soo...yeah) or next to someone literally missing their face.