Prequels with MCU actors (no main actors crossing over like Samuel L Jackson or Natalie Portman..)
Anakin/Darth Vader - Sebastian Stan (right amount of charm and darkness, has a decent resemblance to his on screen son, played by Hamill)
Qui Gon Jinn - Jude Law (looking like young Dumbledore)
Obi Wan - Tom Hiddleston (I can imagine him saying 'hello there', imo he has the right amount of smugness, swagger and likeability)
Padme - Jenna Coleman (she's Bucky's date in Captain America, she plays Clara in Doctor Who, Queen Victoria and Melia in Xenoblade, I can see that)
Count Dooku - Ben Kingsley
Mace Windu - Djimon Hounsou
Jango Fett - Karl Urban
Darth Maul - A stunt man yeah, but Benedict Cumberbatch says his cool lines in the trailers. He only has 1 line in the movie.
Palpatine - Toby Jones (would play it differently from Mcdirmind, but I think he could pull of the duality and hammyness)