I think Nintendo should have worked harder on personal Miis. They are so basic, that the only customizable thing about them are their faces, THAT's it!! sure they can have a solid color half body, but that's it. Its even worse that a hat, counts as a hair design. It would have been nice for clothes and apparrel to make your Mii stand out more.
I don't know of anything about mii, but early on The Wii's release, there was some other software, which I think failed, which could backup your Miis.