"...On one of Ray Mear's shows in the desert, he tied the "sand ladders" (or whatever they were called) to the vehical when getting out of soft sand, so they would be dragged behind and he could wait for a convenient spot to stop and pick them up.

No idea if this approach would be useful on snow..."

I have thought of that myself, and the only problem I see with it is front wheel drive, which many of todays vehicles have. That could require some perfectly placed ropes or whatever, to allow the "mat" to free the front wheels, but not go far enough back to tangle with the rear wheels...