Any innovative solutions for adding more batteries?

AFIAK, the ARV uses a Silverleaf charge controller/EMS. It pretty much handles all electrical interaction with the LiFePO4 battery bank, both charging and discharging. I may look into that, since it has a lot of nice features, even the ability to fire up the vehicle's engine if the batteries get low, so for a lot of people, a dedicated generator may not be needed, especially if the furnace, stove, and water heater are all diesel powered.