Put some panels on top of the rv and then setup heating for the batteries like this :
I used these for heating :
https://www.amazon.com/gp/product/B075WVPP5Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I simply taped one pad on each of the 4 sides of each battery.
I then used these :
https://www.amazon.com/gp/product/B011VGAPOC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
to control the heating pads.
I placed the sensor for each control unit on top of each battery it controlled the pads for.
I believe I have them wired 2 in series on each of the 4 pads but I may have all 4 in series I cant remember which worked out the best.
I set the controllers to 37F turn on 40F turn off. I havent noticed much in the way of shortened battery life with this setup on my lifepo4 batteries.
So far using a infrared thermometer the batteries have stayed above 34F at all times. My batteries will function to 0C and they have a 32F limit on charging with the bms they have. So I have it setup to keep it over 34F to ensure they will charge each morning no matter how cold it gets.
That said it doesnt get that cold here in Alabama with 20F being the normal lows most of the time in the winter.
Even with your colder temps this system should work fine I would think if you can use panels on the roof to put the power back each day.
Also the pads could be used to melt snow on the panels possibly.