By the same token you can offer dozens of arguments why Tom Welling is not going to get it or shouldn't get it that have absolutely nothing to do with his acting ability to his supporters, and they will still offer the supreme argument of "he deserves it" as if that carries any weight in Hollywood.
For the sake of argument let's say that being in another universe doesn't matter, that WB doesn't care about people being confused, that Tom Welling would actually want the part (and I've seen no indication whatsoever that he does), based solely on his acting skill, would he be a viable candidate for a new Superman movie.
I say again no, because in what movies he did star in he never showed impressive talent. When taken out of his element, he didn't shine, he merely made do. Furthermore, he's been playing a version of this character for 10 years and I don't think it'd be that easy for him to completely reassess the character as he would have to for a Superman movie. He thinks about Superman a certain way for 10 years, now in a matter of months he has to completely re-think it.
I have nothing against Welling, I love the work he did on Smallville. If he came out and said yes, I wanna be Superman in the new movie, I would probably even support him. But until he does, I see no reason to support a fan movement to get him the part that in my eyes is based solely on an emotional factor.