I'm not sure if this information
is completely accurate, but at 1200 lb, it's more feasible than 790 lbs. The Roadster's 53 kWh pack was "almost 1000 lbs." as described by Tesla's CTO this video
And these weights may not include the cooling, etc. and of course, not the weight of the trailer itself, umbilical, etc.
I think we may be one generation of improved batteries away from this being a reality...
Ocean Blue SL-e
Per LEAF Spy as of 03/21/18: 11 bars, 230 GIDs, 53.5 AHr on new (04/30/15) Lizard battery (1st bar lost 12/22/17)
Orig. battery lost 4th bar at 177 GIDs, 43.19 AHr, 44.74 Hx, 65% SOH after 45 months