How about allowing people to choose who to kill? Maybe add an option to kill healthy young male adults who may serve as recruits? 
I actually really like this idea.
Another thought along the same lines. Suppose recruitment could be tied to peasant satisfaction with a war. If a realm is at war with a hated enemy then recruitment stays steady, however if the war is unpopular recruitment drops significantly, requiring drafts, which in turn will lower morale and damage production in the realm waging war. This could also go region by region. If a particular region hates the war then their RCs will be just about empty. This makes looting more risky as it could end up flooding the enemy armies with new recruits.
