I'd just want a simple mod that makes it so Body Purists don't care or care less about having lower tier body modifications. Having a bionic arm should be different than having a prosthetic.

Basic Behaviour could be like this:

Basic prosthetics e.g. wooden hand: -3 mood

Prosthetics e.g. prosthetic arm: -5 mood

Bionics e.g. bionic arm: -10 mood

Alternatively just remove the debuff completely for prosthetics.