This sounds pretty alright, but there's no way to control wether the occupied nation is actually participating in the overlords nation siege. Lets say nation A is occupying nation B. Overlord nation is sieging nation X and nation B creates a treaty to help its overlord in order to get unoccupied, then who is making sure nation B actually is helping the overlord nation A? The treaty would have to be an automatic processed thing where once accepted, nation B gets unoccupied automaticly, because if done manually, overlord nation A could just say screw you and not do it, but if its an automatic process, theres no way to control and enforce participation from nation B, so i dont really think this would work

ok this can be done by using the same piece of code that discourages night capping also known as by the amount of people it can be coded so that the amount of people in the siege are part of the occupied nation, in addition to this i think to control wether the occupied nation is doing any contributions or not will be to check if anyone from the occupied nation capped the banner or if they made other contributions such as kills and craftkills this can control wether the occupied nation has done enough to be released from occupation

Honestly that would work and it sounds pretty cool, its a pretty exciting idea so I'll upvote