I think from when the war reached german borders at latest on You can have as much improvised and ragtag as Your heart desires - they even used french tanks and whatever. Any kind of uniform or weapon, vehicles etc, as long as there was fuel and ammo. The reserve army always used captured stuff for training and drill, and that was available in the "Reich".
You might find a lot of pictures online from the "Bundesarchiv"
looking forward to see Your efforts, it sounds very interesting