Speaking as a musician and occasional audio engineer: anything panned hard left or right (i.e. strictly only on one side) is unnatural and probably distracting. The idea of some separation (I'd go for intercom R, radio L, as R is the natural side for the pilot to hear the other people in the aircraft) is an interesting idea but I wouldn't separate them totally. Which in practice means that you won't be able to do it without incorporating a small mixer and that's way over the top for an aircraft audio system I'd say.