well in the relevant time period the only time an "army" would be allowed to walk your land unchallenged is if you had a prior agreement and i dont think any nobles were known for just seding whole armies on scouting missions. the aggression will ahve to be controlled through diplomacy rather than letting anyone just walk anywhere as long as they dont attack.

the already weak ai is just wasting its resources by having a full stack walking around doing nothing while the human player is wisely building armies only when he needs to attack or when their is a percieved threat.

anyway it was jsut an idea that i was thinking about its prob got be refined quite a bit. but i seriously dont like the idea of armies just standing by your city doing nothing for 10 turns and then turning around and walking away. and also Ai armies seiging a city in the center of you kingdom leaving castles and cities behind then affectivly cutting themselves off from thir resupply routes.

unless a province is reached by sea it should not be possible to calth through one enemy province and take the next one. this will also limit the human layer being able to target the just the rich AI provinces effetively bankrupting it before it can make any affective counter attack. of course the sea route is still there for exploitation but that brings in the danger of several ai fleets picking u ships off and sending yout army to the bottom of the ocean.

i'm rambling today sorry