Considering the skills you mentioned, Tharja is married off to Gaius or the Avatar perhaps. The issue with Gaius and Robin give Noire Multiple paths to go down with Gaius making her probably one of the most effect Assassins in the game. I'd rather have little to no questions on what class to be her in and instead make her a Sniper with little to no hesitation, And the most probably Candidate I can think of is Frederick, Stahl, or Kellam