I'd have a big action-y run-around that only makes a little bit of sense, once you stop and think about it. But it would include:
-- Prisoner Zero, who has been causing trouble for the Doctor in the shadoes since Series 5. He's the one to ask the question, which makes him the evilest creature in the universe.
-- The Silence. They'll make one last conentrated effort at stopping the Doctor; Also that one eye-patch lady chick appears in a flashback.
-- Strax, Jenny, Lady Vastra, and River Song are involved in the story
-- Rory's dad would also help the Doctor, to represent the Pond era
-- The Doctor would die because he refuses to answer the question, and then the Silence kill Prisoner Zero while he's in the throes of regeneration.
-- the 12th Doctor's regeneration line/entrance would have him stand up and ask, "What was the question again?" and that plotpoint would be forgotten for the rest of the series.