I spent three years dealing with the poor performance and constant problems with hard wired lighting in my 2013 CRV. The added lamps in the tail-lights were a joke, and the six pin receptacle was a Chinese POS, that I replaced repeatedly. When the CRV was replaced by a slightly newer one, I went to wireless LED tail-lights. Best move I ever made. I will never hardwire another toad again, and in the OP's case, I can't imagine wasting the time and money to hardwire TWO towed cars, when you can end up with a better solution, with no labor and no questionable modifications to OEM wiring, for less than $100. I use the "Blazer" brand from Amazon.
When it comes to "modules" to make hardwiring a plug and play adventure, there is something you might want to keep in mind. A buddy of mine is a really top notch independent mechanic, who works on anything under CDL weight, that rolls into his shop. When he gets a vehicle in for strange tail-light or general lighting issues,he always check for a hitch, and factory four or seven way wiring. If he finds aftermarket wiring, he searches for the aftermarket plug and play module, and remove it. In most cases, the problem is resolved. When I wired my first CRV, he strongly suggested running a totally isolated system, and avoiding the factory wiring, due to failures of aftermarket parts spliced into OEM harnesses.
