With as many miles as you are driving, the V or a V8 SUV isn't going to be double the fuel cost. The V can get 20-21 on the highway. The cars you are currently used to driving are not making 40+ mpg.
There is nothing wrong with driving a V in the winter or 20,000 miles per year. It doesn't make you a bad person to actually DRIVE the V as daily vehicle, and not treat it as a garage queen. The car was MADE to be driver, and it does so well. It does so, both as a fast car, and a comfortable car for long trips. Unless you live out in the country, with huge hills and roads that are not maintained, where the snow fall is going to dump 24" of snow regularly, getting some snow wheels/tires will work just fine.
I have driven 2 trans ams, 1 corevette, 2 SRT8 in the winter, and have had little to know trouble with any of them unless I left the summer tires on.....
The CTS-V might continue to hold value pretty well, but the year of the car is going to depreciate the value worse than the miles. In 2018, just the fact that the V is 8-10 years old is going to have taken its biggest hit. At that point the difference between having 80,000 miles and 150,000 miles on the car might not be insignificant, but its not like you're going to have left it in the garage with 3000 miles either....thats the ONLY way a 10 year old car is going to keep that value. I guess my point is, why buy any car if you're worried about putting miles on it? Cars are expensive to own, insure, keep fueled etc. Cars like the V make it more of a finacial stretch. In the end you don't buy a V, in order to save money on gas, or be practical.
My vote is, if you want a V get it. Throw some snow tires on it before you worry about another expensive car. Why get an SUV anyway, why not some small cheap FWD car? I think you will find that owning the V will make you not want to drive anything else anyway!