As I understand it, early Casitas came that way from the factory (back window AC, not roof AC a la Francesca
). But yes, a person could cut a hole in the FG and route the AC through a wall, or poke it out the
front window for variety.
Many eggs have AC in a front closet.
As for taking the rear AC out while traveling... not sure. Since it's that way from the factory, I'd guess not, but that's just a guess.