Earlier quoted context omitted.
The problem with machinery and trail maintenance is that machinery is heavy, and unless it can wheel itself to your worksite under its own power, it's unlikely going to save you any labor.
It's also straight-up illegal to operate any sort of vehicle in US wilderness areas (horses are OK). I think they also ban gas motors and maybe even things like electric chainsaws.
I have a friend who does trail maintenance in the Dolly Sodds and surrounding areas, and he has gotten quite adept at using a crosscut saw with his partner. I've seen it in action, and the efficiency of that tool, in the hands of skilled users, is quite impressive.