My dream roster would be all the SF3, SFA, and SF2 characters, along with some other characters:

Haggar
Ingrid
Rook (CFAS)
D.D. (CFAS)
Poison
Joe (SF1)
Black (FF3)
Dean (FF3)
Callman (FF3)
Mel
Go Hibiki (Dan's father)
*A judo fighter
*A lucha libre fighter

Yeah, the only way a Capcom fighter with that many fighters would happen is if they made it in 3D and took about 7 years to make it (making it in 2D would be too time-consuming/take too much money). But since CFAS was cancelled due to bad feedback and Capcom barely made any money from 2D fighters anymore after SFA3 came out, it's highly unlikely for them to even release another fighter now, unless it's a rehash.