I have a hypothetical scenario and I just wanted to know what the correct method to approach this would be if there is one at all.

Lets say I have a kingdom with 2 provs, province F and province U.

Province F is a Faery/rogue t/m. Province U is an Undead/Tactitian attacker.

As the age drags on province U announces that he doesn't care for Undead or the attacker role and want's to switch to T/M. Province F offers to switch with him.

How can they go about doing this so the swap is kosher? Is this even allowed at all?

Can they just give each other their login credentials, change email and personal info and that's it?

Or do they, abandon their respective provinces and then get invited to take over the province which they are taking, consuming 2 invites?

Or is it something else?