It seems strange to me to see a discussion like this conducted in terms of only one principle. For example, consider how would we know if someone consented to

It seems strange to me to see a discussion like this conducted in terms of only one principle. For example, consider how would we know if someone consented to being killed? And how could a consent structure for it be abused? This is where we see it bump against another important principle, that we may not deprive another person of their life without due process of law.