While you are that 'deep' into the project.. you might consider doing what we did in a small area.
I purchased some special 'epoxy' called 'GitRot'. It is a thin epoxy which repaired a 'softening area' on our 1999. I will utilize this process whenever I discover a 'floor' issue like this in the future. It would add a bit more cost, but potentially a lot longer LIFE in your AS..
There is another site I recently discovered (by help of a friend here) that specializes in epoxy and where you might consider as a 'source' for your project. PM if interested in knowing more.
Basically, you could drill 1/8" holes partially into the floor along the perimeter, inject the almost "water" consistency epoxy into the wood flooring and this will 'tighten up' and waterproof the area... we have had 3 years on the 'fix' and no issues..! We have had occasion where water penetrated in the same area but, was just a damp spot on top of the epoxy..!!!
We were able to resolve the leaks without worrying about potential 'damage' in the area..
Good job on your Airstream!
Peace and Blessings..