Fair enough! The layer stack is perfectly usable as it is now, and I'll probably go ahead with the multiple-folder solution I mentioned for this particular issue. I will say that a filter search in the states menu would be very helpful if you get around to it, as I occasionally get lost in the layer list looking for specific layers I need to toggle.
Good to know about identical layers not affecting performance, though for some reason the idea of duplicating the entire model multiple times to change expressions is equal parts interesting and hilarious to me~.
EDIT: Wait it just clicked, I'd use folder-toggling states to control my expressions and the "bald" toggle state to toggle all of the hair layers on/off throughout the entire project. Still might be a tad excessive for this particular project, but that is good tech!