What you're proposing won't work because I can't restrict a building to a specific location. In Shogun 2 once you code a settlement building this building can be built in any settlement. While I could make the Hanyang version a building that Korea can only have one of and put this building in the capital the player could simply destroy the Hanyang building and build it elsewhere. This solution also won't prevent the player building country buildings in Hanyang.
Another alternative would be to have Korea start with the Hanyang and Yanggae versions already built and make a technology that Korea can't research be required to build the lowest levels of these buildings. This would prevent the player building these versions in country regions but it won't prevent the upgrading these building. However it won't prevent the player building country buildings in Hanyang and Yanggae areas and it also means that if these buildings are destroyed the player can't rebuild them.
Before you asked I did try to make a unique settlement type where you could only build specific buildings but it didn't work correctly (for some reason when I made a new startpos sll the new buildin ignored.
It would be better to have one version of each building that can be built anywhere and restrict which units can be recruited based on region resources.