the public bathroom should be redesigned so that one can do only the thing it is designed for - and maybe it needs to be a single-user design.

Almost like an airline bathroom size - might be a bit claustrophobic but these are for emergencies and space saving would be big.

the doors could be wired to sensors that are connected to a central network that shows in real-time the availability and also some alarms if something is out of the ordinary etc.