I'd like to see a part of the challenge in conquering the fiefs from the nations/states at first.
This reminds me of my old idea about how AI Villages/Towns/Castles should look like in terms of equipment. What I had in mid was a realistic setting for them, for example: a Castle in the Desert should be buying only Sarranid equipment for its defenders instead of having ridiculous outfits when you fight for em, like: Strange Armor, Knightly Shield, 1h Axe & Nordic Helmet. Same for all other Nations, they should be equipped with their own armors/weapons to look more believable & realistic but unfortunately the Great Donkey said its too much coding for nothing as the aim of the game is to wipe the AI as soon as possible and have pure PvP battles so I wouldn't have high hopes If i were you.
That said - I too believe that taking a Castle/Town should be a challenge and If i was proficient with these things I'd code it all myself.