A lot of great ideas flying around in this post, but I don't necessarily agree with some. Putting limits on how many fiefs a kingdom can concur I feel is a bit too stringent, as well as having tons of units in your settlements isn't to realistic. I feel like one underlying issue is not that there isn't enough men to hold a settlement its that its a little to easy to take those settlements. The devs are going in the right direction i feel with what they've implemented already. But maybe defenses need to a be a bit tougher, cohesion need to drop faster as well as AI's ability to recover from loses and not get caught as often. I feel like more natural approaches would be better than setting hard limits.