I think you maybe over reaching concerning replacing the floor and interior walls as described in another thread you started. Whole scale replacement of the floor will require just about a complete disassembly of the house part of the coach. The very first item the builders add to a chassis is the floor and replacing it with steel really isn't an option. Plus the weight will quickly become a big factor.
The key to avoiding water related damage such as wood rot or delaminating is proactive preventative maintenance. Every hole or access point in the coach, be it side wall, floor or roof, has the potential to leak as the material used to seal it ages. Periodic renewal of the sealant is your best defense. The includes not just applying new sealant but potentially reworking the seal such as complete removal of a window or skylight, cleaning the base surfaces and resealing.
The factories building a coach do an adequate job of sealing it up during construction but it's humans doing the work with manmade products. In other words it may not be perfect and it's not going to last forever. It's incumbent on the owner to maintain the coach in ways that are more than just changing the oil and replacing the tires.
Your ideas have merit but I think with proactive maintenance a coach would last just as long.