lol
You know what would've been really interesting ? For the game to pull off the twist reveal of Venom Snake being the medic sometime around mid-game, and then switch for the real Big Boss for the rest of the missions, and each character would have their own areas and set of missions.
That would allow more gameplay variety, it would give closure for the players, it would allow us to play as the real Big Boss, and it would give us opportunity story-wise to see how Big Boss became what he is in MG1 and MG2 and him becoming a "demon", and show the contrast between Venom Snake and Big Boss.
The last dialogue between Ocelot and Miller seems to be revel in its strange, prophetic revelations. Subtlety, at that point, had jumped onto the nuke and sailed into the sunset manically waving its hat.
It would still work as a meta commentary about the player is Big Boss and makes their own stories, and would echo the MGS2 character swticheroo, only here it would actually be more accepted. As in, "You played a character that looked like Big Boss for 30 hours, so you see, you can have fun even without him".