This is sort of a Vassal prototype question, but it applies outside the game engine. APCs can dig in, as they are also combat units. Transport cannot. Kubels are obviously not APCs, but they are not unarmed either. Should they be allowed to dig in?
I think anything that has a weapon should be allowed to dig-in.....
In fact, why can't we allow anything to dig in? in 30min of focused effort a couple guys (driving a truck) could
certainly put up a berm and get the truck into a more secure position....
So, maybe even transports should be allowed....I'm betting they had a shovel on most trucks.