The initial implementation seems to be OK, but there seem to be certain circumstances where the system fails to consider. Specifically, a situation like this, sort of presents a problem. ... This overall situation in the pic, is what is (sort of) known as "the failure of the Versailles Treaty" in history. Simply put, there is NO WAY IN HECK THE LOSER OF THE WAR CAN PAY THIS MUCH AMOUNT OF WAR REPARATIONS.
I've not yet confirmed just how exactly that "tribute" is paid. But from prior experiences in paying for peace, it is most likely the tribute money comes directly from the pocket of the ruling clan. Then, what happens in the situation where the ruling clan, cannot pay the tribute to end the war?
The war would probably rage on to the end, with no way for the losing side to deal with the situation.
I think perhaps, this might be behind one of the reasons why some kingdoms get engulfed in wars against multiple opponents, without being able to end the previous war -- and it needs some looking into.