In WW1, many tanks came in two or three versions-a cannon armed "male" version, a machine gun armed "female", and, for the British, hermaphrodite tanks with a cannon sponson and an MG sponson. Males focused on blowing up machine gun nests, females stopped them getting swarmed by infantry. I'm interested in keeping this split alive past WW1.
Now, obviously, unless you want to end up like the poor Matilda, something with a bit more bang than a single .30 is going to be needed. Autocannons(or at least a whole bunch of .50s) would be the order of the day.
Examples like the various flakpanzers, M42 dusters and the BMPT terminator show that AFVs armed with autocannons weapons can be very useful against infantry and light vehicles. However, with the exception of the terminator, these are repurposed AA vehicles, often deployed in AA battalions. Female tanks in WW1, however, were used in integral units with "male"(eg cannon armed) tanks.
So, let's say some exercise in the interwar period reveals that tanks are vulnerable to close range attack by infantry, or to air attack or the like. Some planner/tank designer decides to slap some machine guns or an autocannon on a turret of a standard tank. These "females" would be one or two of the tanks in each platoon, tasked with mowing down infantry, light anti-aircraft duties and maybe dealing with AT guns by slaughtering the crews. Probably a bit daft, but that's interwar tank designs for you. Then Mr. Hitler invades Poland.
How effective would this doctrine be? What country would be most likely to develop it? What chassis and guns would work well for such a design? How might it develop post-war(Helicopter Gunship Destroyers?)