IMO if this is added, you should be required to have unlocked/acquired the GM poring by normal means first once on master account. Given how much goes into acquiring the actual pet, being able to go out an get a regular poring an skin it as a GM poring seems.. a bit unfair?
Maybe I'm wrong - but the GM poring doesn't actually do anything, does it? It's just a badge of honor.. so doesn't having a skin of it kind of defeat the purpose of getting one by normal means? If I'm wrong, that does change my opinion though, I just don't see any more info on it.