If you have a nation as a vassal, you can build their UUs! And in return they can build your UBs 
I think it would be fairly historically accurate. In the past, the colonizer would often use the military units drafted from the local populations, giving units more ethnic flavor. And in return, he would build his infrastructure buildings in the colony.
I think it would be fairly historically accurate. In the past, the colonizer would often use the military units drafted from the local populations, giving units more ethnic flavor. And in return, he would build his infrastructure buildings in the colony.
