We already know the concept of "person" is bankrupt unless you allow degrees of personhood (unless you are content with an ethics that has no problem with torturing dogs, but forbids saving 2 people using the organs from one brain-dead death-row convict with a terminal disease that gives his vegetative torso one month to live).

My ethics has the concept of personhood in it and doesn't allow degrees of personhood... but I don't think the brain-dead death-row convict with the terminal disease is a person. (Because they're brain-dead, not because they're on death row or because they're terminal.) Are you making the error that all humans must be persons for all definitions of "person"?

(I also have a problem with torturing dogs. My entire ethics isn't about persons.)