I camp all the time in winter here in Norther Ontario and although a battle hardly the end of the world or even close to impossible.
I camp with the system in full operation in a rig barely 3 season campable by KZ. It does have a decently insulated and coroplast covered belly, with all walls and floors being about R7.
I have electrically heated pads on all the tanks and heat trace on the interior water lines.
Heat is mostly provided by three ceramic cube heaters doing "zone" heating with the propane furnace doing all the grunt work to get the rig up to temp and maintain it should the temps drop more than what the electric heaters can maintain(I have camped as low as -30C/-22F)
In so far as dumping the tanks I do that at home with a Flojet macerator. Don't need a clean out, just a convenient toilet if that is all that is available.
Lot's of other tricks to keep the cold out and the heat in from Relectix in the windows, carpets on the floor, heated mattress pads and so on. Also having at least a 3kw generator with you as well should power fail due to storms, which up North in my neck of the woods happens quite often.
It's not impossible, just challenging.