I suppose Sherlock telling John to make sure if everyone knew that he was a fake could have been to protect his friends from Moriarty's assassins, but I don't think so. I don't recall Moriarty asking for that. That's why I think he must be using this as a bid to take over Moriarty's gang and destroy it. ("Hey, you know this group commits real crimes, but the Sun was right that Moriarty was just an actor I hired to front my operation. Now do as I say.")

I'm skeptical that the solution will live up to the mystery. It didn't in Moffat's other series.