A one-sided hitch? I'd like to see how that works out, especially how it handles the lateral forces, and the large torques at the points where it's fixed to the bike. You obviously have it all figured out.
As for snow-ploughs, admittedly my trailer only turned into one when the snow was too deep to actually cyclke through. Still, fine adventuring. I wouldn't discount 12" wheels on 'snow-plough' grounds.