This is pretty bunk, dude. Not that you're wrong, but bunk in the sense that this is portrayed as a fault with the series, something it's failed to accomplish, rather than one of its fundamental themes
The tragedy of Big Boss isn't that he becomes a bad guy, it's that he strives for an ideal that doesn't exist. After learning the truth about the Boss' defection, what he wants is to prevent another soldier from ever being the victim of political machinations again.He establishes Outer Heaven so soldiers can simply be soldiers, without being bound by the wills of suits and desk jockeys. But what he fails to realize is that there's no such thing as a neutral act of violence. A soldier fighting for Big Boss is no different than a soldier fighting for the Soviet Union. He becomes the thing he hates the most.
Snake Eater is a story about, above all things, perception. Remember that this was the first in the series to introduce the little thing where you can press R1 during cutscenes to see events through Snake's eyes. In doing so, we're given some extra insight into his character, even if it's just a jokey little bit where he's staring at Eva's chest while the Ocelots surround them. While it seems kinda small and insignificant, it's actually important enough that his eyes become one of the defining aspects of his character. His entire arc is illustrated through the first person view. MGS3 is a game where we see the lives of soldiers as through the campy lens of action movies(specifically modeled on James Bond and Rambo) before the facade is ripped away and we witness the true depth of their suffering. It's a campy action romp that ends as a tragedy. Honestly I think the way it plays with different tones is pretty genius.
The most important series of events in 3 is Snake's capture, torture and escape culminating in the boss fight with The Sorrow. The torture (In a microcosm of the whole game, the torture is first concealed behind a veil before it's gruesome nature is revealed) is the most graphic in the series up to this point, and there's certainly no way to "win" it like before. In Snake's cell we meet Johnny, who is actually somewhat of a warm and comforting presence. Johnny provides a humanity to all the enemy soldiers you've been facing thus far. He shows kindness to Snake, something rarely shown happening between opposing soldiers. Then the fight with the Sorrow confronts you(not just Snake, you) with your actions thus far, trying to make you rethink how callously you dispatch your foes. Now press R1 after all this happens. With his eye missing, Snake begins to quite literally see things differently. Most of the hidden R1 segments from here on out involve The Sorrow, the specter of death is shown to be guiding his every move. Snake doesn't kill Volgin, he's fried by a random bolt of lightning(summoned by the sorrow, natch). He's still beholden to forces beyond his control or comprehension. The final image we see is a POV shot of Snake tearing up as he stands before The Boss' grave. His vision is clouded here, just as his judgement will be. Literally and figuratively, he cannot see past his own pain. He is more or a less a slave to the traumas of his youth. His later ideals aren't based on any pragmatic view of what war should or shouldn't be, but just a personal desire to not be hurt in the same way again.
The important distinction between Big Boss and Solid Snake is that they're inversions of each other. Solid's story in MGS1 was all about him defying his "programming" and moving on to forge his own path despite what his genetic code(nevermind that nothing anyone in this game says about genes makes no fuckin sense, it's all metaphor) and the manipulations surrounding him were supposed to predetermine for him. On the other hand, when we meet Naked Snake he's still young and naive, but we the players know that in the future he will become a villain. In essence, his future is predetermined. Solid took what he learned about the world and used it to form his own set of values. Naked let them possess him and drive his every move. Moreover, Solid's eyepatch in 4 is on the opposite eye.
Metal Gear Solid 2 is about the folly of idolizing Solid Snake, and the danger of wanting to emulate him. The Solid Snake in this game is not the in-universe, canonical legendary soldier of Shadow Moses, but instead the video game character Solid Snake of Metal Gear Solid. And this video game character tells you not to take pixels at face value, but instead question who put the pixels there and the meaning behind them.
What I'm saying is, for Big Boss in MGSV to suddenly take charge and be the sole master of his destiny would contradict his entire character up to this point as well one of the series' main thematic conceits. Because well, being an independent man of action is an honorable and noble virtue, which is incompatible with the series' notions on war and conflict. War is a violation predicated entirely on lies and deceit, and participating in it of your own volition isn't meant to be admired or glorified.
holy shit this is long. sorry if this all seems out of order, i could ramble about mgs for a while.
