I have noticed there seems to be two reactions to Welling's unwillingness to wear the Superman costume.
1 Screw Tom Welling!
Recast the part! (that is never going to happen within the context of this series folks!)
2 Adjust the costume to Welling's whims! Show it briefly!!! YEah that will do the trick! (But that misunderstands his reasoning. It appears that he does not want to actually be seen as Superman in any shape or form. A blur flying away maybe all we get)
Unless he has been bluffing all these years or drastically changes his mind, few fans are going to be satisfied about with how this series will end.
That is my prediction at least.