You said the delamination is where the camper sits in the truck, that means the basement. The slides are not very close to the basement and should not come into play regarding placement of the aluminum plate.
Use of the plate would actually be stronger than the OEM board.
Replacing the vinyl floor would be easy, and would not require removing the slides, unless you believe that the entire vinyl floor should be replaced including the part that you never see when the slides are out.
All that is required is to remove the base boards and glue new flooring to the existing vinyl, or remove the old vinyl and place new vinyl on the bare floor.
I did talk to Host this morning, and they basically said that you did not want the fixes they proposed and wanted everything new, even though the some of the fixes would make the camper last longer.
It looks like it is a matter of expectations. The warranty is very specific in that it is up to Host to decide how to fix.