Why shouldn't I go this route? (AC Roof Delete)

Bus Grease Monkey on youtube put some sort of heat pump system on his personal bus a couple of years ago and was real happy with it.

Of course he had a little more room for the unit and the solar paneling, as he has a BUS.

The reality of this discussion is you're not going to get anything but armchair quarterbacking and naysaying, as nobody has experience with doing what you are trying to do. It's not like installing fender flares.