Outside the SF2 cast, I want Alex from SF3 (and the whole SF3 cast from Ultra), R. Mika from Alpha 3 (I don't care if Ono supposedly hates her), Eagle from SF1/CvS2, and Viper and Juri from SF4.
I'm also not completely opposed to bringing back Ingrid from Capcom Fighting Jam/Alpha 3, but only because I enjoy her gameplay.
Guile
Ken
M. Bison
Gouken
Cammy
Dee-Jay
Yun
Yang
E. Honda
Blanka
Rose
C. Viper (but change her gameplay, no more herp derp)
Juri
Akuma
Dudley
Ibuki (no more vortex please)
Zangief
Urien
Q
Gen
Alex
Guy
Cody
Maki
Cammy
Karin
Plus, let's say 5-10 new characters. The roster is going to be huge no matter what.
-Don't go all MUGEN on the cast. SFIV has too many characters which means too many match-up possibilities and in inevitability some of those match ups just aren't very exciting b/c a disadvantaged character has to stick to one strategy and one strategy only to win.
-Find a way to get the Arika char designers from the EX games on board. Diago is pretty good but only C. Viper and Juri stuck out from the new designs and I don't see Juri being too timeless a design. The char designers from III, EX, and Alpha (whom I'm guessing had some of the same designers as III) really knew their stuff. Get one of them to partner up w/ Diago and let it rip.
If they can do that I don't care who they throw in as long as it's some ridiculous crap like Oni Akuma or Evil Ken or w/e, leave that for MUGEN. Bring the cast a bit more back down-to-Earth, keep the count intimate, and surprise me with lots of new innovative and SF-feeling character designs.
I'd love to see the characters aged up to 2015*, but I doubt those Ryu and Chun models are just placeholders. Capcom's going to play it safe with the roster and stick to barely-aged SF2 era characters as the core after the disaster that was the SF3 series and the success that was SF4.
I think fans would accept an aged Ryu who more in control of himself (like Gouken). Mel Masters could take his father's place and Chun could have her own disciple (one of the kids she adopts/teaches in the SF3 story). Bison could very well still be around, in a different body (that of a doll?) if necessary. That way the classic style could largely be preserved while also freshening it up.
*SF2[T] takes place in 1993, SF3:3s takes place in 1999. SFV taking place in 2015 would mean core characters would be 22 years older than their iconic portrayals. Ryu would be around 50 years old if the timeline was consistent (and Sakura would be in her early 40s).
I hope Capcom embraces its reputation of disappointing fans by creating a fresh, divisive entry where the only returning characters are Ryu and Chun-Li.
Don't listen to the fans, Capcom. We don't know what's good for us.
Bring back Charlie and Rose for sure. Its time for a dope Silat fighter and maybe a Billy Blanks homage Tae bo figher also for kicks (no pun intended).