I was looking for info on the Desert warfare during World War II and I saw pictures of the Jock Columns with guns being mounted on civilian trucks.
I said why not and here is my intent at a civilian truck that could be converted to fit the theme and that could be used by militia units.
Since I did it with pen and paper, it might be full of mistakes but I know you will correct me.
Support Vehicle
45t
Tech rating D
Chassis: 7t
Speed: 4/6
Engine Weight 15t
Fuel: 1.5t
Range: 1,000 km
5 additional seats: 0.5t
Armour: BAR 4 1t
Front 11
Left/Right 9
Rear 9
Cargo: 20t
I could imagine an anti-'Mech/tank variant with an AC/10 facing the rear or a flak variant with twin AC/2 in a Turret with no armour (I know it is not legal but it sounds kind of cool).