Most vehicles already provide green cover for troops. The main reason you don't see people use this is due to the nature of vehicles needing to move to survive against ATGs/ranged AT.
Well, ATGs being fielded before any vehicles can feasibly built does have a lot to do with it, but that was sort of my point: a hulldown ability could give halftracks a bit of durability. Enough at least so that one could absorb an extra blow or two could make that cover viable could make all the difference.
But furthermore, the fact that infantry scatter at the slightest twitch of movement has another thing to do with it. Having units stay in cover is a rather important aspect of utilizing its benefits. It'd be hard to use the cover even if you tried.