This Matchbox truck was spotted lurking in a poundshop wearing a garish green livery, with an orange inflatable boat on top.
The boat went straight to YesthatPhil’s AK47 navy and the truck was given an office body to stand in as a Luftwaffe ground control truck. I don’t think that the Luftwaffe developed the same sort of large caravan-bodied vehicles that the British did for air traffic control. The example below is a workshop vehicle, and seems to be about as large as they get.
My conversion looks nothing like the real thing, and is a bit too modern, but in the absence of any accurate information, it will do for now.