Thanks, that's helpful. I'm actually not "judging them with the purpose of choosing one to systematically follow" -- my interests are more theoretical than that (e.g., I'm interested in what sort of moral theory best represents the core idea of Consequentialism).

Having said that, I agree about the importance of counterfactuals here, and hence the importance of agents following a theory rather than merely conforming their behaviour to it -- indeed, that's precisely the point I was wanting to highlight from Regan's classic work. (Note that this is actually a distinct point from systematicity across time: we can imagine a case where agents have reliable knowledge that just this once the other person is following the CU decision procedure.)