IMO
From Alpha : Karin , Cody and Guy
From 3rd Strike : Urien,Q and Alex
From SF4 : Abel and Juri
IMO these characters definitely deserve to come back in SFV and i like their intresting gameplay styles :3
I personally would like:
-Oro (ex supers were great and they’d look amazing)
-Akuma (closer to his 3rd strike incarnation. [ including firey raging demon win-pose)
-Fei long
-Juri
-Alex (come on capcom -___-)
-Hakan (too pimp to be denied.)
-Gen (coolest old dude in a fighting game imo)
-Blanka
-Mokoto (Badass women ftw)
-Zangief (Hugo’s just kinda “meh” to me)
-Dictator
-Urien (greattt moveset)
-Cammy (I hate her but whatev, I need somebody to hate in a fighter lol)
-Either boxer works for me 
-Skullomania (neverrr used 'em but people seem to love the dude lol)
As for the freshmen, just pleaseee do not make them over-the-top goof characters 
and super difficult secret boss fights are a must.
Personally I hope the following make it in.
Oni
Seth
Akuma
Gen
Oro