These are only photo "replicas" that are being made, not actual Muppets for use on TV so I don't see using different materials as being an issue just as long as it looks good. The Kermit replica was advertised as made from "similar" materials not the same ones. Whatever they choose for Gonzo's nose and ultimately Piggy's face will be fine as long as it looks good at the end. They don't need to use the same materials, especially if it means the replica will have a relatively short shelf life.
I think using antron fleece for Gonzo's nose would be fine as long as they get it the right colour and shape. I would prefer this to the rigid nose idea.
Once again guys, I'd like to add that we should be happy that these replicas are happening at all and for a very affordable price!