Hi, another way to go regarding Home Guard etc. could be to say that flagged terrritories has a notional unit (yes, I too come from a WiF background) with a defense value equal to the PP value of the territory.
So 1-5 is what to roll equal or under for a hit, a 6 equals a hit, more than 6 equals a hit + a chance for one more. So for Ruhr, it is 1 hit and 1-4 for one more. This unit could not be taken for losses and fires only in the first combat round and only the first time the area is attacked.
Positive: no more units needed and restricted influence in combat with many units (except perhaps US that has few and high-numbered areas, maybe max out at 10?)
Negative: remember which area that has used it´s notional unit. Especially in Russia if the war goes back and forth will be troublesome I guess. Anyway, only a suggestion.
Daniel