Phil, thanks.
1. It is possible to through load cca. 2 pairs of skis under the rear seats, but it is annoying to have part of skis in "a living room" interfering with cupboards. I suggest to use a roof box.
2. The fridge is the main consumer of electricity, the aux heater is less problematic, so we can easily manage to stay without a hookup 3 or even 4 winter days with the heater on most of the time (cca. 14 to 16 hours per day). I am still impressed about the concept of 2 aux batteries that I found as one of the strongest points of a Cali.
3. In alpine countries the dedicated winter tyres are obligatory so we don't even think not to have them. Yes, I am running on 4motion with snow chains as a backup only. However, if you plan to visit major resorts you shouldn't have problems with 2 wheels drive & winter tyres most of the time.
4. .... it is a little bit general question, but I would be happy to answer more specific issues.
My general recommendation would be - not be afraid of winter camping, it is a pleasure to do it with Cali down to -15C when some more annoying issues occur, most of them due to lack of a serious insulation. But it is rare to experience even more brutal temperatures in the Alps below 2000 m.
Oh, and there is one more thing.... The Airtronic Eberspacher aux heaters in our Calis work at altitudes up to 1500+ m. They are capable to work at higher elevations for shorter time, but for a serious winter use at some of the highest mountain passes or resorts in the Alps, you should upgrade it with the original Eberspacher High Altitude kit.
I did it through an Eberspacher service and I don't regret -
http://www.heatso.com/eberspacher-high-altitude-kit-22-1000-33-2200/