Keep In Mind This Is My Opinion
Republic Classes
Jedi Knight: Human
Jedi Consular: Miralukan/Mirialan
Trooper: Human (Just Because I Grew Up Seeing Most Troopers As Humans)
Smuggler: Human
Empire Classes
Sith Warrior: Sith Pureblood (Human Would Work Here Too, Just Because My First Sith Warrior Was Human)
Sith Inquisitor: Zabrak
Bounty Hunter: Cyborg or Rattataki
Imperial Agent: Kind Of A Tie With This One, Chiss and Rattataki