New trailer, or if you have payload capacity to spare you could try self leveling compound and putting linoleum over it to level the floor. Replacing the flooring isn't really an option IMHO since they're integral to how the trailer functions. I've seen some Airstream frame off restorations to redo the flooring and even though they're made about an order of magnitude more stoutly than your typical TT they're still unbelievably fragile when not tied into the flooring, they're also worth a lot more so it's easier to justify the extreme labor cost.