I'm still not expecting those Japanese yahoos to make such a deal and abandon the UN. That would go heavily against logic. They might try to sell Zero, for sure, for a good price like Japan, but that doesn't mean they would suddenly leave the UN. Because it makes zero sense (no pun here). If they leave the UN and thus the UN would get crippled, Britannia would crush the other nations and then come back to Japan and crush the BK lingering there, alone. So what if there was some deal? What are they going to do? Sue the Emperor?

It would be a victory, after a fashion, for the UN if Japan was reclaimed with a deal. After that they could concentrate their forces on some other fronts. War does not miss one man, the saying goes. Sure, Zero was behind all this originally, but I doubt the other UN leaders would simply surrender to Britannia if Zero disappeared.