You can easily understand why some classes are immune to occupation. For example it would be chaos to resolve what would happen if a Butler occupied a Butler, who’s would go first? Others are for balance, like blocking the King would be too powerful. But some are immune for little reason.
For example, Hunter does not need immunity. If you occupy it, it should just not use bear or wolf. If drunk debauches it while on wolf, they would be immune to the attack. MM can also survive being not immune. It just fails its convert/probe. Blocking a Prince should be fair game to stop executes. Some classes might need target changing to function as an occupy, else Prince executes someone random since Invoker controls him, and it would make no sense to bear someone else. But it feels like a a lot of roles are immune, making it harder to play Butler/Drunk/Alcoholic/Servant.