Questions about Home Guard/Militia units..

[Legbreaker]

That's pretty much it in a nutshell.

[HorseSoldier]

5) Gun trucks built primarily from commercial vehicles (dump trucks the most common and easiest to convert) will be the most common big armored vehicles in most areas.

Sounds like a plan in places where you have a good supply of machine guns and other automatic weapons -- and dump trucks, since I'd think most places would have a lot of non-military use for functional dump trucks. On the plus side with a dump truck, however, you could probably up armor the cab and then make everything in the cargo bed removable -- some brackets to hold a frame keeping a double stack of sandbags in place on the sides, weld on some weapons mounting points, and if your need for a dump truck is greater than your need for a gun truck, you just pull all that stuff and send it to the job site or whatever.

[Legbreaker]

How about a flat bed or container carrier - build a removable "bunker" using a shipping container as the base and lift it onto the back of the truck when it's needed. When it's not mobile it could be used as a pillbox.

Would have to armour up the cab a bit, but if done right, the armour could stay in place even when the fighting unit wasn't loaded.