Currently the only real way to make money is to trade, and taxes are really just used by large clans to discourage others from taking their SD.
So, to make things more interesting and to help us focus on war I suggest the following:
Have villages only produce raw products… say hides, fish, grain, wool, grapes, iron, wood, livestock, pelts, olives, hops and clay. These are sold at the cities, where people could own workshops that turn them into leather, dried fish, bread, cloth, wine, tools, lumber, beef, fur, olive oil, beer and pottery.
Every city has a market place where these products are gradually purchased by the populace, driving the prices up. Anything that is not produced locally has to be imported, and of course some local products will be exported.
The village owners get 75% of the sale of the raw goods, while the delivery guy gets the other 25%. City owners get 50% of the finished goods price and the workshop owners get the other 50%. Traders make their money by taking advantage of price differences between cities.
A village produces raw materials based on its population, so if it is attacked it won’t produce much for awhile. And, if an enemy does grab a village, he won’t be able to sell locally, but will have to bring his goods to the nearest friendly city he can find that has the right workshop.
One thing that sort of is required is the ability to bar clans and individuals from trading in your cities. Being able to lock the door so to speak.