A very similar concept is Revoy, which hitches a device between the tractor and trailer. I expect Revoy's model would see a much higher utilization rate (time spent driving or charging vs sitting idle).
This seems like a neat idea. But it looks like it also adds an extra pivot point and length. Are most commercial drivers trained to handle these and would they normally have the proper endorsements for such trailers?
That was my thinking as well, in Australia this would be a b-double tandem, requiring extra endorsement (multi-combination license).