I live in California so I'm no expert on freezing weather, but it seems to me like you could drain the water tank and get as much water out of the lines as possible with your low point drain, and then run an electric space heater in the motorhome. I don't know if you can still get them, but years ago I bought an electric heater at West Marine that was designed for use in a boat. It has a freeze protection setting on the thermostat. In this setting the heater kicks on when the temp drops below 40 degrees. I use this when we are going to have freezing conditions in California and I don't even drain my water tank and I've never had a problem. But then again it almost never gets below about 25 here either.
Another alternative is just leave your motorhome in the South and drive the toad home for the few weeks in the winter. It may even be cheaper to this versus using the fuel to get back home.
2021 Nexus Viper 27V. Class B+
2019 Ford Ranger 4x4