I understand not wanting to deal with added bureaucracy. I'll have to see if there are any regulations like that in NM. I doubt it. To answer your question about intended use, I intend to use the trailer on forest road and fire roads. But, that is my intended use now, things can change. I don't want to limit myself when I have the opportunity not to. And from the safety perspective, I'm sold.
Etrailer has some video of installing the brake controller on an FJ Cruiser. Looks simple enough.