I would agree with your assessment. Cold weather packages are really more for late autumn rather than for actual winter use. I have also thought about putting a small space heater underneath with the ability to plug it directly in to the power pedestal rather than using up the available camper power. I'm not sure you would have to add any ducting to it. I also thought of using a line voltage thermostat in the circuit to keep the basement just above freezing. I currently have my underbelly cover off to add a second water tank so I bought some 1/2 pipe insulation and am going to insulate the water lines. In my case I don't plan to live in sub-zero weather I just want to extend the season.
Seasonally in the Grand Marias, MN campground
On the beautiful shores of Lake Superior
2012 Ram 2500HD CTD