... but I have no idea where on earth I would put such a thing.
You have the most "stuff" on a camper/truck rig than most here. I suspect that if you got the itch you would find a way and then the rest of us will see the pics and think, "that is soooo cool. Why didn't I think of that."
But you need a catalytic heater so you can heat the camper proper like and not use up your charge. I'm an ice fisherman and spend all day out in the wind and cold (and love it really) but to come back to a "home" that is 38? No. ... just say'n.
And I have an argo that I trail ride in the same mountains in the same winter in the same state as you. 38 degree camper? No.
I wear merino wool against the skin, wool middle layers and an outer layer that both insulates and floats. I know how to layer. 38 degree camper? No. I don't care what Eddie Bauer invented in 1940. (An interesting reference to technologies past by the way)
Live in a 38 degree camper or run a semi trailer sized generator sipping locomotive quantities of high grade gasoline? I'll run the generator. (of course I probably wouldn't go, it's just a visual...)
If you don't like the idea of a Wave or Buddy, get the PlatCat - it exhausts to the outside for a tiny fraction of the electron potential cost and has a thermostat. You need it. 38 degrees... Sure, it's the high end for the recommended refrigerator temp at your local eatery.
Solar or Gen?
If you AC or use a toaster a lot (or any device that use a lot of resistance heating) then you must use a generator (or a farm of PV panels bigger than your truck...) The AC runs the most just when you want to be charging the most and will probably out compete the sun. The devices just eat amps.
If you camp in the clouds or dark places or just don't want to dig out the panel from the snow or watch blueray on the big screen with the PS3 then you probably need a generator.
Otherwise, there are ways and devices to make your electrical needs very small so that you are in the range of PV. Led lights, efficient compressor fridge, catalytic heater and you are pretty golden.
For the record, I don't care how you camp. If you like the PS3 along and munch toast while watching movies all day then that is fine with me. I've done it myself and may still. (But personally, only in certain places where I feel I won't bother my neighbors.) In general, the small modern generators don't make enough noise or fumes to bother me all that much and I've found most people with them are far more aware of their impact on their neighbors than the average camping dog owner.
For me, the idea of always ready and easy setup leans me towards the simple PV setup for the camper in the truck. It isn't the only camper that I have. I may add AC down the road (I can do cold weather but hot weather just is not in me...
) and then I will size that so that it will run on the EU2000i that I already own.
Get a small generator so that you can lock it inside the truck or camper. I have had 2 larger/cheaper generators stolen right out of the truck. Chains cut and all. At meal stops!? [Edit: this last bit here is meant for "If you get a generator..."]