I like your idea better.
Arm everyone.
Have an organized militia as well, for when needed. Have special units trained in mortars, RPG and shoulder launched SAM launchers. These guys would have extra training than the regular civilian “infantry” militia.
Maybe you could even have pre-placed Militia Stations scattered in the neighborhoods, small warehouses, where they park, er, pre-position the heavy trucks and armored vehicles and heavier weapons. These could also be the local neighborhood Militia Headquarters.
Farther out at fewer installations would be the larger radar and SAM sites, the heavier armored platoons and then still fewer would be the various, well-hidden airstrips. The higher the tech-arms tree the fewer there are and the more “professional” they are.
There is no reason any enemy would have to be able to figure out where the orders are coming from. Maybe there is a bunker, a cave or maybe the bosses are calling it in from their bedrooms.
Having a decentralized force has a lot of benefits, as well as costs. These scattered HQ’s could have ammo and supplies stored but how long can the fighting last before they run out without resupply, a week or two?
Inventive resupply.
Make your opponent resupply you, unknowingly hopefully.
Or just out and out gank one of his supply columns with those overly helpful civilian towns behind the lines.
Kinda like entering a village in an rpg, everyone seems nice, and then in the blink of an eye the kids are playing soccer with heads while the women play didgery doo with knives in navels as the whole town falls in on the intruders.
Total Resistance by Maj. Hans von Dach