Like Baalka, I see this as more of an evolution of the battle tower in Divinity 2, a home base that you can build up and have an influence on (directly and indirectly). I understand your point about immersion, but having a different area in a game world filled with magic doesn't seem out of place to me (nobody complained about fortresses build on giant rock floating in the air in Divinity 2, though there were some about the main character not taking fall damage).
