Yep, once it is out of your hands, it's best to forget about it and let the new owners do what they will. Because they will do whatever they have a mind to do and nothing you say or do will change them.
I frequently contemplate buying a steel cargo trailer with no roof vent and no rear door, and building it out as a TT. I could have a vent on the rear wall and a mini split A/C. Order the trailer with some steel attachment points welded to the roof, and mount solar panels up there without having to puncture the roof.
Mike G.
Liberty is meaningless where the right to utter one's thoughts and opinions has ceased to exist. That, of all rights, is the dread of tyrants. --Frederick Douglass
photo: Yosemite Valley view from Taft Point