I understand that the way this is set up is designed to prevent gamey behavior (among other goals I'm unaware of, no doubt). It is presently resulting in very gamey behavior.
Terran has fallen. The invading army is very far away and doesn't want to conquer the land for themselves; instead they struck a deal with the Duke of the capital (me) to establish a new realm. The capital can't secede, so we had the option of temporarily joining another realm (so that we wouldn't be the capital) but that was deemed too gamey - i.e. 'we aren't actually changing allegiance to you, we're just de-capitalizing ourselves and we'll be gone in a week.'
So we convinced a neighboring Duke in Terran to secede with the idea that we'd then pledge to join them, since we previously had the option of pledging to another, neighboring realm even though we couldn't secede.
Neighboring Duke secedes and we go to pledge only to get this message:
'You cannot change allegiance with the last city in the realm.'
If the intention here is to prevent gamey behavior, the only solution I can see is to force our new neighbors to conquer us. Terran has no ruler, and I won't run for ruler because it will kick me out as Duke if I do.
What is the solution here? Do we just appeal to Tom to please switch us over to another realm? Do we force people who like us to 'conquer' us and spend two weeks TOing several regions?