Okay what if enough people become independent? I had a game in the CoK scenario (playing as the Night's Watch) where the Iron Throne just...dissolved. The crownlands were split between the KitN and Shireen Baratheon, lady paramount of the stormlands. therew were kings in the reach, the westerlands, and the iron isles. Dorne was independent (emperor-tier) as well. I loaded as Robb and Balon and they both had the decision "declare kingdom of westeros" available to them.