Hearsties, I agree with almost all your points. Armies steamrolling across the map and making one faction dominate makes the game absolutely unplayable long term, which sucks because I really want to devote a long playthrough to one character.
On the army system, I don't think the concept as a whole is bad and needs to be nixed, I like it more than a roving band of lords following a marshal. The issue however, is armies function like well drilled and organized machines, not a band of squalling nobles who shouldn't all be so happy working together. Lords should break off from armies more often. Army cohesion should be more difficult, and armies should require larger food stockpiles to feed men as well as all those massive amount of horses lords no doubt have, making it much harder to keep an army in the field for weeks on end smashing castle after castle. Implementing all those changes would help fix the army steamrolling issue.