Check the "flat plug" circuitry
Depending on the OEM wiring circuit, the flat plug idea may or may not work.
On some autos three or four diodes will be required.
They run about 10 bucks apiece.
If the extra set of running lights is acceptable, or if there is a place to mount temporary lights dedicated to towing, then a separate light system is, IMHO, is the way to go.
"Looks good, doesn't cost much, lasts a long time."
"Suck it up, spend the bucks, do it right the first time."
WBCCI # 1113
Trailer '78 31' Sovereign
Living Large at an Airstream Park on the Largest Lake Totally Contained in Texas
Texas Airstream Harbor, Inc.