[Richard]

Simon has the Dometic split units, so no internal ducting.

IF I had that setup and were committed to converting to modern day technology, I would seriously explore the mini split world. Essentially the Dometic units in those coaches was a mini split of the day with external compressor and condenser, and internal air handler and evaporator. The point is the space and electrical is already there. The trick will be finding something in the modern era mini split world that will fit in those spaces with minimal modification. You could also use the existing line set runs. They should be good for the higher pressures of r409 or r410. I wouldn’t try to use the existing evap though. In my opinion retrofitting into the existing space would be more better aesthetically than trying to find two locations for a wall mount cassette.

The roof top conversion wouldn’t be terribly difficult, however the challenge would be adding Newell appropriate ceiling design to duct and hide the overhead. In the coaches of Simon’s era, he would lose 5 inches or so of headroom to have it look appropriate. Given the care and detail that went into his magazine shoot worthy remodel, I doubt a standard rooftop panel in the ceiling is going to make the cut.