You're so right that trailers can be made much lighter and many today are but a trailer that can be towed by a small Toyota is going to be pretty tiny for a family of 4 or more on an extended camping trip.

I say go for both. Sure there's the potential for tricky handling in adverse conditions but that's easily handled by being able to shut the system on or off or simply decrease the amount of boost. I certainly don't advocate the trailer completely propelling itself, just enough to offset some of the weight. Hell, a 747 can land itself these days. I can't imagine not being able to design electronics that could respond quickly to varying conditions. Electric motors are pretty amazing creatures that can have their amount of torque changed instantly by pretty simplistic electronics. Sensing devices such as accellerometers, pressure sensors, inclinometers, etc have become extremely accurate and inexpensive these days.

The biggest problem is see is the question of the towing vehicle's suspension. If that trailer gets to bouncing on uneven surfaces, it can impart a great deal of vertical tongue weight on the hitch which would be a problem. That might be a deal stopper.

Art