Love, Prolly.
1. It would be titled Love, Prolly.
2. Benedict Cumberbatch would play David (Hugh Grant).
3. Martin Freeman would still play John, — yes, the character's name is John.
4. John and David would cross paths briefly, and there would be some kind of subtle Sherlock joke.
StudioCanal
5. Billy Bob Thornton would still play the President of the United States.
6. Eddie Redmayne would take a break from all his Oscar-winning dramatic roles to play Colin (Kris Marshall).
7. Sam (Thomas Brodie-Sangster) would have a different, more modern motto when he learned the drums.
StudioCanal