The only thing I would say about that is that I remember the composition (rubber) floor that was installed in my high school. The first install had an issue with the glue, and it didn't stick. They had to tear up the whole floor and re-install a new one.
If I were taking that sort of plunge, I would see if I could get a small sample to experiment with. Wood is very porous, so the glue penetrates the wood. Steel is not very porous, so it will be much harder for the glue to stick. Usually when gluing to steel, one uses epoxy, rather than a rubber based cement.
As far as the idea of using a rubber floor, the material its self is very tough. I still have some scraps from my old high school. Recently I cut up some small washers for my transmission mounts. It has held up better than any of the OEM washers.
BTY: If you get that level of water intrusion into your coach to damage the plywood floor, that damage is going to be the least of your worries. The walls will detach from the floor, long before the plywood floor rots. Usually they use pressure treated marine grade plywood for flooring.