Right now youre thinking that I dont have a creative bone in my body. Here is why I think Jack would be a great companion. Peter Capaldi is incredibly inappropriate. Now, Doctor Who is first and formost and forever a childrens show in Britain, even if, as an American writer, I dont see it that way. If Moffat were to make it anything else, Britain would revolt. So, Jack Harkness is a companion idea for Capaldi to a certain extent. I will be honest and say I dont know all of the events of Torchwood: Miracle Day, but I can imagine, based on what I do not, that its possible that for a few episodes we would have two people, the Doctor and Jack, who have known each other longer than any other companion, leaning on each other for support and making sure theyre okay. They slowly will be able to help each other back to where they used to be. Not to say that the Doctor will be less dark or gritty, but no one understands his loss, I think, like Jack. It would be interesting to bring Jack back not as comic relief, but for who could honestly understand the Doctor has gone through. Meanwhile, Jack may need reassurance of the Doctor and what he does, and who he is. A season together (with limited innuendos), may be what they both need. A friend. Reassurance for Jack about his friend, and a friend who cant die for the Doctor. Also, this would massively contribute to the multiple characters played by Capaldi.