Boris Gudenuf
Deity
I mentioned above that Plague Doctors (unlocked in the Medieval Era) could upgrade into the Medic in the Industrial and then into a Supply Convoy turning them into a Medical Support Unit class with the latter two also able to heal military units, like they currently do.
Two things help this formulation: first, military and civilian medicine had a lot of 'cross-over' from the Medieval Era on as they were dealing with many of the same diseases of over-crowding (either in a city or a military army encampment) or trauma and second, in virtually all military establishments after the Renaissance (first 'modern' armies in Europe in the 17th - 18th centuries, for example) medical support was administered by the same supply establishment that brought up supplies like food and ammunition. Complete militarization of both was amazingly long in coming (not until the late 18th and mid-19th centuries, depending on which army you study), but it means that Medical Support can be part of Military Supply and also Civilian Epidemic Control without stretching any of the terms too much.
An elegant solution, since, presumably, a Plague Mechanic in the game would also affect both military units and civilian 'population points'.