I don't care either way who the backup will be. I guess it would be kind of cool to see Vince Young on the roster, just because of who he is (and because of Madden speed).
But, based on comments from Nix on the John Murphy Show Friday, I think Vince Young's performance in practice will have no bearing on his roster spot, good or bad. Nix said that he plays well in games, despite often poor practices.
I would say that, unless he throws numerous interceptions and incompletions in the preseason, he will supplant Thigpen as the number 2.