I think Artisans at villages would make villages more interesting. Basically, the artisans would consume items bought from towns and make rare/unique items for the player to consume. Yes villagers only sell items, most food to towns. We need items to give bonuses to villages (like tools to speed up hearth creation)
I think requiring resources for settlement upgrades would add more immersion and feels better than just dumping gold. Or perhaps, allow the resources to speed up construction of Castles? I think there is something in to be found in the middle here. I also don't think its a grind, its more of a money sink.
I think Tournaments should be expanded then. To allow for Kingdoms to compete in peace time, a non-war related thing to do. Joust, Melee, and Archery. I think it would be better than the general tournament.
Claims and casus bellis could be implemented, but not necessary for war. There could be just wars and unjust wars that affect loyalty of settlements afterwards. Its just for flavor, wars are so arbitrary and random, and its all there is to do in the game currently. Just thinking of ways to make it more immersive. Claims could also be used to get more votes from the AI for war, etc etc.
I like the idea of paying for materials to build stuff, you had to do this in viking conquest if you wanted to build ships. Which was really rewarding grinding for that first big long ship. It would also be a bit more of a money sink for those who complain theres nothing to buy and gold becomes too plentiful. Could make it so AI lords also have shopping lists for this, which would affect town economy based on whos buying what to upgrade at the time.
The Artisans are hit or miss. Maybe a couple through out Calradia, for spice, and discovery, but every village already produces something "Unique" in the sense they make trade goods. Yes there are other villages that do the same, but they are spread out mostly. Couple Spice vendors, Tea houses, etc that offer a rare (Only 1 or two locations on the map) to buy these.
The Idea of Castle tournaments with 1v1 jousting (1v1 horse back in a stylized arena) and archery contests in that you need to shoot X targets in Y time, or hit X targets with out missing, and they could just program the AI to have specific accuracies for these tournaments that are semi-randomized in difficulty (Peasant, Novice, Capable, Intermediate, Master, Grandmaster) and make a pool for who is capable of what. IE T1 Troops can only ever be Novice/capable. T2/3 could be Novice/Capable/Intermediate and so forth. Lords tending to be Master/Grandmaster, or have it related to their own archery skill. Tie these semi-thematic games with the long awaited Feast mechanic! So now its not just a dinner party, but a 2/3 Staged event. With the player being able to select the agenda. IE Jousting, Archery, Duels, Feast, or just Duel / Feast, and vice versa. Depending on how extravagant you want it to be, the more you pay, and more activities you need. You could also ask Lords/Ladies to play the various board games while at the dinner party. Over all just a big improvement on immersion / Character building with other lords.
Instead of winning money, or a Tournament Prize, you gain reputation, and influence, and the person holding said event gets prosperity added to their estate? This would create another money sink in the fashion warband did with having to fetch food, and exotic trade goods.
I also agree that Noble troops should be hired in Castles, and perhaps the feast function mentioned above could also give the Notables of the castle more power, with which to get noble troops more frequently (Use big lavish parties to attract all the young Noble warriors to your house for recruitment).