If you want villages to have increased importance how about giving towns a money-income based on it's "connected" villages, and require money for raising/maintaining troops. Probably towns should have some level of income from itself so they're not fully dependant on villages, and also to let you tune the level of importance of villages by adjusting how much of a towns income comes from itself and how much come from the villages.
Historically, even castles with very low number of garrisoned troops were never (or at least hardly ever) ignored by invading troops, for fear that the troops would be able to disrupt supply-lines to the fighting armies. Even very low number of troops could do considerable damage to an army if they were bypassed, by disrupting the supply of food and other necessary materials.
To model this, you could have some level of attrition (simulating desertion, etc) of armies fighting in areas with unbesieged hostile castles in them.
Some other ideas:
- Raiding parties. Small-ish parties roaming enemy areas, reducing income to the controlling town while they're around.
- Patrols, primarily for keeping raiding-parties at bay.
- Razing villages, and burning them to the ground rather than attempting to capture-and-hold. Probably villages should be allowed to be rebuilt aver a period of time after being razed (the most valuable part of a small village would be the farmable land, and crops, most of which wouldn't be destroyed by razing the village).