If I were writing the first episode, it wouldn't have anything to do with "The Time of the Doctor". It would be a standalone story set on present day Earth, where Clara has to defeat aliens while dragging along a less-than-helpful post-generation Doctor.
Well, we DO know that Clara met up with the Prime Minister, getting whatever clearance level, some time before TDoftD. We even saw pics of that. The Doctor wasn't visible in them.