Wireless would be a dream come true. Mount the wireless transmitter in the top front of the trailer, hardwired into the invisible trailer truck plug, along with the electrical/brake wiring. Then having the camera being a wireless receiver, with a quick mount, on the exterior of the door/trailer back wall. Not complicated at all, I just don't know enough on how to carry it all out.
On most trailers, this would be pretty much unobstructed, except for the thickness of the rear door, pure "line of sight". "Piece of cake".......
Sure would be nice if GM and a Trailer Manufacturer or major trailer parts supplier could get together and come up with something.
AAhhh, to be young again and dream...