Even if they play nothing alike anymore, I have a difficult time justifying Guile in the initial line up when we have Nash. One weird-haired sonic boomer is enough to start with. Guile can feature into the story, he doesn't need to be starting lineup for it.
I'd be so bummed if they revealed Guile. I mean... I really hope that's not an option.
As you say, Nash fills that spot perfectly, and he looks more interesting to boot.
Vega is already bit of a disappointment for me. He looks cool, but he's not a very exciting pick.
I understand the need to win the old crowd first, but I find the "classic" characters extremely boring in general. Never had any desire to play Vega, Blanka, Balrog, etc.
I'll be content as long as there's one unique 3S character in there. (Please be Urien.)