In locomotives the electric motors are just the way to transfer power to several axles, where pack of transmissions and differentials would be too complicated.
You have full size engine, full size generator and no batteries to give driving power.
Again the fully electric power for driving buses is on the roads for over a decade. It is only the concept where the energy is coming from.
Obviously putting electric motors to push motorhome wheels and than install 300HP diesel with 225kW generator would not make much sense, but 100hp generator and battery pack that would get most of the power from solars would be very nice.
This way when you take motorhome for grocery run, the diesel will never start.
But to get enough power for highway driving you need huge generator, or huge solar.
