Re: Reinventing the wheel
I don’t know of any slam dunk search term, but I suspect that the discussion you want to have surrounding partial preferences will contain mainly similarities to the work done on ceteris paribus laws. Particularly, if we aggregate the partial preferences of all moral agents, we will produce something like a moral ceteris paribus law, where we are holding the set Z of background variables “unchanged” (i.e. within a “reasonable” range of values). You might find the discussion around the justification of CP laws useful.
Additionally, I believe there must be some relevant work on the application to morality of modal logic and possible world semantics. I don’t have something to point to here, but it might be a worthwhile direction.
That’s right, only (Defect, Defect) is Pareto dominated in PD and Chicken games