I wonder if you could put in a trailer wiring harness that just plugs into the harness in the back and just run it to the front.
You know the kind that just plugs into the harness with a t in it that goes to the rest of the harness and then the t part goes to the trailer.
The system would be dead until you plug into the motor home, then live.
Not sure so don’t take my word for it, check it out.
This site may be helpful, not sure. There is a search button on the top that may be of some help.
http://www.etrailer.com/faq/wiring.aspx