I second most of these suggestions. Warband is rich in "so what?"- moments. After long campaigning I get my own castle, after long courting and being hated by rivals I marry my wife - and then there's pretty much nothing it does but stand around and look somewhat nice.
I'm definitely all for children: you could even retire and continue playing with your son or daughter! Also, more politics is nice.
Great fan of the house functions. A training yard would probably be rather simple to integrate, it would just use the scripts for those training areas on the map in a castle-like area. Visible training/mock-fights could be done like the practicing soldiers in Gothic, just standing there and repeating nice motions. Storage seems simple enough as well, although it would add a great deal of atmosphere if you could actually place weapons and armor on the racks and see them, though that probably won't happen.
Seconding watching tournaments and visible building upgrades.
Religion seems highly interesting but I think this is difficult to put in and would require a lot of thought. But I like the idea of having temples in the cities.
