Im only really saying all this because I never used castles in Shogun and Mongol Invasion, ever. Even though this new game is supposed to feature castles as the central player, I think that unless building protection is improved, you won't be able to use castles in challenging games.

I was used to playing on expert in STW, and while it wasnt that hard to beat, if you let the AI do things like wreck your improvements, things could get ugly real fast.