4. The Time War
Yes, we all know he was there when Arcadia fell and saw enough to make him want to end it all with the help of a big red button, but beyond that very little is known of any bigger role in the Time War and its aftermath, in whichever timeline you choose to believe. Legends tell of him leading the Time Lords into their biggest battle and it would be fascinating to see, hear or read of his career as a young officer in the defence of Gallifrey. Possibly even in a forcibly conscripted sense given his previous antipathy towards his own species? Which opens up a whole other debate as to who could play the young War Doctor. Suggestions are welcome, but any list of nominees surely has to include Benedict Cumberbatch. The younger face briefly seen post--regeneration in'The Night Of The Doctor' looks a bit like a composite of Cumberbatch and a young John Hurt, and the man gracing Sherlock seems the type to be able to pull off a combination of compassion and steel. All of which of course depends on the timeline. If he goes on to make his home planet go boom we could see him sow the seeds for his older selves with a certain degree of repentance fighting alongside a push to accept it as the only righteous course of action. If we're shown glimpses of the Moment begging him not to use it in all its sentient glory back on Gallifrey or indeed elsewhere before the events of 'The Day Of The Doctor' that could also be a massive game changer for the wider universe. How many more species and worlds could be roped into the conflict, and how many more would die? A definite philosophical poser and enough to give Mr Cumberbatch plenty to chew on and deliberate over.