“The stalls are in fact individual rooms (walled off from floor to ceiling), with a shared area with sinks & mirrors.”
may work for normal people, but for a person with devious intent - fully walled stalls (as I have seen in some store/resturaunt restrooms) can be unsafe for the normal customer.
If used at off peak store hours a woman or child can easily be followed and pushed into one and assaulted.
Also if a person is using the fully walled stall alone and has a medical issue, how will anyone know? It would take much longer for another customer coming in to notice, probably until the next time employees clean. Or if the lock gets stuck for young or old user and they have trouble getting out?
It isn’t perfect but preferable to the free-for-all alternative. If need be, have a screen outside the bathroom showing the common area.