Just my personal opinion, but I really hate the whole "ritual/planned" warfare thing. It's just a way for the unmotivated and bored people who are too risk-averse to fight a war, to pretend that they're fighting a war. This doesn't fix any problems.
I think it'd be more risk-averse than most wars if it was fought over the right to sacrifice nobles. Most wars are fought with the assurance that your character will live unless they're an unlucky hero. Without that? A lot more uncertain.
