If Ul'Dah does get changed into a republic, they could let the Sultana keep her title as an honorary one with no real power, just cultural significance, and have her actual position be akin to that of the Japanese Emperor or British monarch. This game IS Japanese, after all. What they're setting up to happen in Ul'Dah is setting the city-state up to have a nearly identical government to Japan's current one: A parliamentary democracy with a figure head cultural monarch that has no real power beyond cultural aspects and ceremony.

Doing so would maintain the status quo for quests involving "the sultana," "sultansworn," and "sultana nanamo" but change the status quo for the story itself.