A large LiFePO4 battery inside the coach safety concerns?

To your safety question: IMO, anytime you have a containment of high energy, it should be enclosed so that any catastrophic failure can be somewhat contained. I'd think a metal tool box would be fairly appropriate.
FWIW, I have five batteries inside my trailer, 3 AGM's and two FLA. The FLA batteries are in their own vented box and the AGM's are inside a cabinet enclosure.