In my opinion, while I initially was opposed to unique castles, thinking they were out of place, I think they give DLC civs a lot of character. Making the castles generic for the DLC civs kinda gives them less character, and also makes them less accurate. The Bohemians, Bengalis, and Romans in particular do not feel like they represent their cultures as accurately with the generic castles, which don’t fit them.
This idea could be done the other way around as well.Castle age castles are generic skins imperial skins will be these new skins.
Even monasteries can have a different look in each age pagan looking for castle and generic for imperial for some.