Would kinda explain why it's being done in two parts as well. You can't exactly play half a game, then be told that none of it actually happened. Also if it actually happened, it'd be a weird twist on what people were saying about MGS4. "Metal Gear Solid 4 was nothing cutscenes, it's practically a movie." And then this happens.
What if Ground Zeroes, the first half of Metal Gear Solid 5, is a film made by the Patriots to glorify Big Bosses actions taken at Camp Omega? We already know that Decoy Octopus was an actor before he was taken in by the CIA, so could it be him? Is that why it’s Kiefer Sutherland instead of David Hayter? The images below are what kinda set me off and theories are fun, so why not.