A guy needs to be able to plug his BEV/FT (battery electric vehicle/flat towed) into the RV and have driver controlled dynamic braking/regen/charge available when under way.
The BEV uses dynamic braking to first top off it’s battery (aka regen mode) then to grid heat inside the RV during cold weather travel and or charges the RV house batteries, then to the RV water heater, and finally when all else is topped up the excess braking energy is wasted to atmosphere through a grid heater like a locomotive.
The tech already exists see “locomotives, downgrade”
Of course 27 kinds of connectors will be needed because a Tesla to a Tiffin will be all different than a Rivian to a Winnebago...