Wow, lots of great advice and opinions. I did find out that Tiffin (and others?) used to add extra batteries with the residential fridge, but in the past few years they (and pretty much all manufacturers) just put in 2@12V. Same thing you can expect in a $15k travel trailer, so much for "high end".
Adding more batteries is an OK idea, however, you cannot just put them on the floor of a basement bin. Those bins are pretty thin; OK for lawn-chairs, not a bank of batteries would be way too much.
Aside from the technical challenges, I have some heartburn about paying $150k for a new coach and then needing to do major modifications just to keep the fridge running all night.
Sigh.