I agree, the whole concept of unions is failing because of the non-replaceability of the kings. If a king merges early game and quits in between, the kingdom is now broken as the vice-king can no longer leave the kingdom while the governors are free to do so. A king from a premade in com1x3 tricked a king to enter a merge and immediately deleted xD.
I guess they can give us the normal 1 king game back with 10k treasures per new treasury rule. That should be good instead. The 10k rule adds some new dynamics to the game and decreases the WW dependence.