So you can imagine yourself in someone else’s position, then say “What B should do from A’s perspective” is different from “What B should do from B’s perspective”. Then you can enter all sorts of game theoretic considerations. Where does morality come in?
There is no “What B should do from A’s perspective”, from A’s perspective there is only “What I want B to do”. It’s not a “should”. Similarly, the chess player wants his opponent to lose, and I want people to feed me, but neither of those are “should”s. “Should”s are only from an agent’s own perspective applied to themselves, or from something simulating that perspective (such as modeling the other player in a game). “What B should do from B’s perspective” is equivalent to “What B should do”.
There is no “What B should do from A’s perspective”, from A’s perspective there is only “What I want B to do”. It’s not a “should”. Similarly, the chess player wants his opponent to lose, and I want people to feed me, but neither of those are “should”s. “Should”s are only from an agent’s own perspective applied to themselves, or from something simulating that perspective (such as modeling the other player in a game). “What B should do from B’s perspective” is equivalent to “What B should do”.