From a former FWC owner (loved it) who tried the winter camping thing (wouldn't do it again), here's my advice before you pull the plug and buy a pop-up for winter use.
First off, your going to need some materials to try this out.
A tent, Mr. Heater (or other moisture producing propane heater), cook stove, a set of saw horses, and a 4x8 sheet of plywood.
Before the next cold snap and snow storm, set the plywood on the sawhorses.
Set up the tent and put in the heater.
When you get back from skiing, or whatever you do during the winter, put all your cold, wet gear in the tent. Crawl in, crank up the heater, and cook dinner. What, no way to vent the moisture from cooking?! Get used to it, Sally.
When your done, go to sleep (did I mention in the 'materials' section that your going to need an extra blanket or two? No? My bad.)
In the middle of the night, get up, out of your 3 layers of blankets (yes, the heater is still on) and pee in a bottle.
In the morning, drag yourself out of said blankets, knock condensation from breath, propane heater, and cooking off fabric walls onto everything. As you wait for coffee to brew be sure to keep wrapped up in blankets (yes, the heater is still on) and dream about a warmer camper.
When all that is done, its time to "lower your camper". Remember the plywood and sawhorses? Yeah, this is where they come in.
Go out, squat under one end of the snow covered plywood and lift. Legs, not back! Lower. Move to the other side and repeat. Note: if you don't get an FWC, your back may not feel this exercise, but I bet the lifting mechanism of the camper will...
If this sounds like fun, then your well suited to winter camping in a pop-up, enjoy!
1999 Dodge Cummins 2500, QCLB, 5spd, 4x4, stock
1990 Cascade 8.5'