3. He's A Young 55
Age does play a big part of this Doctor, which is why I keep mentioning it, but it's not a bad thing. Capaldi is 55 going on 40 and will not completely play his age. His Doctor will at least somewhat match the age he's supposed to be while still turning on the boyish charm if he needed to. William Hartnell was 55, but was made to look like an old man. Capaldi doesn't have to worry about that. Hartnell was an old man, but the youngest Doctor. Capaldi has the rare chance to be an old man playing an old Doctor. That provides so many opportunities for the character to develop even further. Maybe The Doctor will start realizing that he's reaching the end of his lives and will need to think before he acts.