without insulated ducting your thermal efficiency would be pretty poor. that said packing all that around and keeping it useable and out of the way would be more hassle than its worth.
Why not just mount the window unit in the wall ( front, up high if possible) you're not hauling in and out with all its crap. Our first popup had a window unit in the side being the axle, hanging out all the time (made for interesting towing at times) later removed, made a sliding tray the window unit mounted too, and a door that opened to slide in and out as needed.
the most transparent option, RV roof AC, expensive, but aways out of the way.