That would sure work, Herk, but you have then added potential failure points (only if the hitch actually breaks and the system is needed), including the diode and its connections. Also, you then don't achieve the on-road "applied brake" monitoring function.
Should the system actually be needed and not operate, the accident re-constructionists and lawyers would have a field day, I'm afraid!
In the same vein, is there not a "breakaway switch" periodic test requirement of some sort? The switch itself could fail, the cable could become brittle enough to not be able to pull the pin out, etc, etc, etc.......
My switch is looking like it might need to be replaced (just old), and the pin was really difficult to pull out when I ran a functional test last month. The pin looked like it was designed to NOT be able to be pulled.