Do you have any changes in mind towards sieges? I'm not a 16th century Japan-student, but siege warfare doesn't feel extremely historically plausible atm. Currently almost every siege is a first-turn assault, and usually bringing some archers and katana samurai suffices to take a castle, it feels too easy sometimes.
So, apart from the increased garrison sizes mentioned in the first post, do you have a specific opinion on how hard it should be as an attacker to take a fortress (even with only a garrison present), or on the ratio of starve-out sieges/siege assaults?
Anyway, this looks very promising, I'd like to try after my exams!