Thanks for the suggestion. My main concern with the approach you outline is if I need a valve to preclude the possibility of refrigerator combustion gas getting into the cabinet and then the living space?
Regarding the purchase of a unit designed for external venting, the space available is very restricted, it is 22" wide, 12" tall, and 15" to 20" deep because of the curve of the MH.
I was not able to find a unit that would fit in this space which was intended to be built in and connected to a vent.
Regarding you suggestion to place the unit on the stove when in use, I don't think that would work for us. It's not unusual for us to use the stove and microwave while preparing a meal. My wife wouldn't be able to lift the unit in and out of the compartment it would be stored in (they're heavier than a microwave), and she wouldn't like having to ask me to move it for her whenever she wanted to use it (or the stove).
Your idea of plugging a fan into a switched outlet will be easy since the microwave outlet is already switched (The rig has an Air Conditioner/Microwave switch).
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama
1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border