I did what you are asking about on my 1958
AS 18' Traveler almost 2 decades ago. I had a small area at the rear where a window had previously leaked where I repaired it as well.
West Systems Epoxy is a great product that is easy to use with the metering pumps. I used Denatured Alcohol to thin out the first coat to ensure that the sub-floor could absorb as much as possible. Then I just rolled and tipped two more coats to seal all. With the newer trailers having rot issues on their sub-floor this made perfect sense to me as a preventative measure.
I tried a couple of Vinyl Planks and wasn't happy with them probably because we can have extreme temperature swings where I live. I settled on Smart Core because it has a rigid core. When I talked to their tech support I was advised to glue it down. I used Liquid Nails Polyurethane adhesive because it wasn't very permanent but did the job very well. I used it with small dots similar to the way Corian Counter Tops recommends so that there is still a possibility of expansion and contraction movement.
Here is a link to the flooring that I used....not cheap but then it still looks great after all of this time.