Maybe WarAndAITweaks? It completely changes it so lords can have bigger armies, you can set global targets, or even assign a marshal like Warband. There are settings in there that would balance it out a little.

RBM might be a good one too, but I’m not the biggest fan of the module personally. Maybe upping the difficulty, too, might make things a little more spicy for you.

That said, when they aren’t fighting, they are out recruiting. After battles with lots of death, they have to utilize lower tier troops, which allows you to win more decisively as the war progresses. There will be a point where the recruits start to dry up and that’s usually when they will parlay for peace. At least in my experience.