for the /source/*/roll angle that is not used at the moment (correct me if i m wrong) because it has not effect on perception if you only consider a source point, could it actually be used to “rotate” the virtual arc on which are the stereo pair - so then it would offer another way to change spatial perception with that parameter in the case of stereo source, (only in the case of non planar system). maybe you already thought about it?
Hum… Not totally sure about that.
Rotating “the virtual arc” (i.e. changing the spatial positions of the two elements of the stereo pair) is not the same as rotating the radiation pattern of the element(s).
Or maybe I misunderstood your point.