Some way for pulseaudio backend to control sink volume

If i understand correctly, right now pulseaudio backend calls the external volumeupdate function and also updates stream volume.

I'd like some way for the volume control to be on the sink volume, either by adding e.g. the external volume option or sth for pulseaudio backend so that it doesnt read/write the sink volume but only uses the volumeupdate function or by having it read/write directly to the sink in some way.