How about allowing people to choose who to kill? Maybe add an option to kill healthy young male adults who may serve as recruits?
Or we could have recruit figures increase by factor 10. Instead of drafting, say 50 men, you'd now draft 500, so the longer a war drags on, the bigger the strain on the population.
I like both these ideas, but they don't really address limited wars. They seem to limit war in general.
