The whole thing weighs 440 lbs.
It's supposedly 3500 watt.
A quick Google of 3500 watt gensets shows a rough sizing of 2ft x 2ft x 2ft and 120 lbs.
I'd rather set the genset on a receiver hitch mounted platform and eliminate the extra weight, cost, and complexity of that trailer.
The backing-up solution is clever but I suspect not foolproof. I'm certain the driver can't see it AT ALL (I can't see my Harbor Fright 4x8 trailer); of course a couple safety flags would help (considered putting one or two one that trailer).
It would be entirely too easy to forget it's there and back it into things. Also it was demonstrated on nice level asphalt; I suspect things would not work as planned on worse surfaces.