I think a Parker Posey or Elisa Donovan type would be cool for a Female Doctor.
If a male, I'd like to see a McCoy sort of manipulative and on a quest to resolve some old thing type Doctor (Not going to make real predictions, as I don't know small British Actors well)
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?