Marvel Veterans (I've avoided picking the more obvious ones like Wolverine, Storm, Magneto, Dr. Doom, Deadpool etc. who are - hopefully - most likely to return regardless of polls):
Gambit
Psylocke
Omega Red
Capcom Veterans (same here: avoiding - hopefully safer - picks like Wesker, Vergil, Jill Valentine, Amaterasu, etc.):
Ruby Heart
Amingo
Captain Commando (+ crew during super)
Marvel Newcomers:
Fin Fang Foom
Spider Gwen
Moon Knight
Capcom Newcomers:
Regina (Dino Crisis) (with dino's appearing during special moves / supers)
Black Tiger (Black Tiger)
Talbain (Darkstalkers) (perhaps combined with MVC veteran B.B.Hood during supers, like her chasing Talbain with her guns or something?)
...
Really difficult to select just 3. For Capcom veterans (Son Son, Jin Saotome, Hayato, Batsu, Rashid, Juri, Alex, Ibuki, Phoenix Wright...) and newcomers (of which I also could have easily picked more like Higemaru from Pirateship Higemaru, Leo from Red Earth, that pink ostrich or green plant monster from Battle Circuit, Leon from Resi 4, Gene from Godhand, Asura, Skullomania (if Arika would let them) or Vile from MMX) especially...
Edit: I've changed one or two choices because I keep going back and forth on them. Sigh...