Well, as a alternative it could use a spindle drive that you crank by hand - like they did for decades in the past. I don't really see why you would have to change the height of the shield all the time, at least if the surface that you are clearing is fairly level.

Well, one option to make up for the lack of weight would be, to tie the vehicle to something like a tree or so - if there is one. But then you don't need a vehicle mounted electric winch for that, a portable chain winch would do the same job. And it always works... :)