I think the problem with that idea is that in BattleMaster terms, that is what militias are. They're perfectly ordinary units, of regularly-trained soldiers, that happen to have been left in the region (or originally recruited into the region) as guards.
I'm definitely interested in the idea of having militia in the game that are more like what we would actually refer to as "militia" in the real world during the period, but I don't have anything very specific in mind yet.