Castles are dead and empty there is as little as possible going on, wait actually, there is nothing going on
THere is no people walking around, no merchants not option to train or hire troops, no option to do anything except besiege it with a silly one ladder or one siege tower of one type, when compared to multi where you have several ladders, couple siege towers option to breach the gate..... makes siege much more fun and interesting with broken buildings!
When at peace there is only VERY few soldiers guarding the city walls, it seems so dead and empty
Way to improve it (by me)
When sieging plan your own assault, divide troops who goes for ladders and where they're going to be, who goes for two types of towers and where they're going to be and who goes to crush the doors (more siege gear = longer preparations)
Add merchants, not all like in city but one or two (with option to built their shops)
Add blacksmith, increase trade income, makes unlimited arrows for defenders "repairs" eqquipment upgrading it to higher quality (from players inventory for a price)
Expand court, at this moment we can have at most prisoners (not much interaction) wife and chancellor, thats very poor
Add marshal who garrison troops, sends patrols to defend villages
Torturer (to beat to death those annoying lords who happen to get into our hands)
Treasurer, to manage taxes, buildings and income