You are correct that FRED class A's never seemed to catch on. Not unlike the Workhorse UFO rear gas engine coach.
The idea of a diesel engine in the front was interesting, offering the torque, fuel efficiency and durability of a diesel engine without all the added costs of a diesel pusher. It would seem they would be noisy but that would depend on how well the coach builder insulated the coach floor and dog house cover.
IIRC, Tiffin was perhaps the only coach builder who embraced them. I don't think Winnebago offered any in their class A coaches.