If I could make a rather far-off suggestion for towing camper/trailers.
Would it be possible to build chassis for campers/trailers that would encorporate the Tesla batteries in the same way as in the cars?
The camper/trailer wheels could be powered and provide assistance in the towing process.
Furthermore, since the camper/trailer floor space would be large, the battery capacity could be large enough to supply the car itself with an extra source of power.
Campers especially would be ideal as they are normally hooked up to an electrical source at a camp site for extended periods of time.
Between the added power to the camper wheels, plus providing a large, external source of power for the car itself, couldn't this mean driving very long distances and maybe heavier payloads?
Maybe employing a sort of mobile Powerwall technology could help here as well.
Just a thought anyway.