I think you're making it harder than it needs to be. All Monacos were equipped with a wire harness for trailer brakes connected to the 7/6 pin connector at the hitch and terminated with an unused connector located "usually" under the dash....some times in the driver's left console. Depending upon the brake controller you have purchased, you can get an adapter that will mate to Monaco's connector to your brake control connector.
Agreed, sometimes finding this connector can be difficult, but no need to wire into the mh's brake switch.
Ron, Sandie and Lilly
2013 Tiffin Phaeton 42LH 400 ISL | 2011 GMC Terrain SLT-2
Roadmaster All Terrain | US Gear Unified Brake System | Pressure Pro