(This got long. It’s mere speculation. Started as just a paragraph, but.. oh well. I guess you could say this is fanfic? All copyrights are to their respective owners. No infringement was intended nor should be inferred. The Earth is flat.)
If I were writing Avengers Infinity War, I’d do pretty much what Scott suggests with the Black Order. I’d have the bulk of the film be about four or five of Thanos’ henchmen split the twenty or so heroes into manageable chunks of five each. The present day is a bunch of action and fighting and keeping the good guys on their toes and distracted. That’s what’s going on the surface. It would intentionally look cheesy and shallow on the outset, and I would kill off certain characters in the opening act of the film: Vision (mind stone), Doctor Strange (time stone), and whoever’s connected to the other stones. I might say Loki put the reality stone in Scarlet Witch’s froot loops retroactively, but nitpickers would probably claim that’s not possible. The Collector coulda sold it to Loki. Anyway if I could swing that, I’d have one of Thanos’ henchmen kill Scarlet Witch and rip the reality stone out of her gut. By the end of the first act, Thanos has all the infinity gems and puts them on his gauntlet. Then he disappears again, after tasking his henchmen to keep the other heroes busy and keep him updated on any information about them that they think might be useful to him.
Interspersed with the action would be seemingly random flashbacks of four or five seemingly random characters. Natasha Romanov comes to mind as an example. In the flashback we’d see her early in her villainous career. We’d see the moment that changed her: when Hawkeye gave her a second chance. First, we’d see the moment as it happened in an alternate reality, which leads to her capture, facing multiple murder counts and eventually her execution. Then later in the film we’d see it replay again but differently. Remember, this is interspersed with battle scenes between our heroes and Thanos’ henchmen. With little to no reveal of Thanos himself yet. However, in Hawkeye and Black Widow’s past, the second time the audience watches her flashback play out, Thanos himself appears and changes one critical detail. Now, instead of being handed over to the authorities and sentenced to the fullest extent of the law, Thanos disguises himself as someone Hawkeye would trust, and talks Hawkeye into giving Black Widow a second chance. Natasha Romanov knows Thanos saved her life, and is in his debt. So before she even meets Steve Rogers, Thanos recruits Black Widow as a part of his family. She becomes a sleeper agent, charged with befriending the Avengers and working for SHIELD until Thanos calls upon her. This sends shock waves through spacetime, dramatically changing reality in butterfly effect ways that rock the battles going on in the present day, and even events that transpire after this Infinity War.
Because Thanos doesn’t just do this to Black Widow. He selects four or five other “heroes” who are among those fighting his henchmen in the “present.’ He goes back in time and changes their lives in ways that turn them into thralls serving his purpose. Not through brainwashing. He changes their lives for the better, and in return he demands their undying gratitude. The gauntlet teaches him who these people are intimately, and how to guide their younger days to become people who want to serve him in his present. People steadfastly loyal to him, who will kill or die for Thanos, by their manipulated choice. In fact they learn the only choice they have is to serve Thanos or cease to be.
Perhaps Thanos goes back in time and saves Ant-Man’s marriage, ensuring he will forever be loved by his only daughter, and in return for that undying love, Thanos demands Ant-Man’s servitude. Simple enough. However, this would mean the entire Ant-Man film now never happened. At least not the way we saw it. Or maybe it did? Perhaps Thanos disguised himself as Luis? That doesn’t really matter now though, as you will soon see.
Perhaps we learn in an alternate timeline, Vibranium didn’t originally land near Black Panther’s ancestral home. In a previous timeline, Thanos visits T’Challa’s ancestors and sees they lived in powerless squalor, then he goes back even further in time, finds a small moon with some Vibranium on it, and throws it at what will become Wakanda. The meteorite crashed there because Thanos willed it, thus giving Wakanda the power and influence to become a power on the world stage, and in return for that favor, T’Challa now owes Thanos his fealty. This may or may not alter whatever’s depicted in the Black Panther film. Again, this won’t matter soon.
Thanos goes back in time to vulnerable times in these people’s lives and finds their weaknesses, then exploits them, thus building an army using the power of the Infinity Gauntlet, as his henchmen battle them. He learns their names and where they’re from, and the gauntlet shows him where and when to go to alter their lives to serve him. Perhaps we even see Thanos try to twist Steve Rogers and Tony Stark in their respective pasts, but it doesn’t work on them, because Rogers is too pure, and Stark is too self-centered. This means of course Thanos has no choice but to make sure they die.. and oh they do die. I would definitely kill them both off in battle at the end of this movie.
Speaking of which, back to present day in the film, it appears our heroes have dispatched the henchmen and thwarted their plans, not knowing their plans were really just stalling tactics. The good guys now know where to meet Thanos himself and pay him a visit. Of course it’s a trap but what other choice do they have? They arrive at the appointed time and place only to be met with one single message obviously left by Thanos so that all the heroes see it at once: “NOW.” The audience knows by now who Thanos has turned. This is very deliberate. In that instant, the five heroes who Thanos has turned attack the rest in intimate personal ways that are quick and ruthless. For who better to take down a foe, than your enemies’ best friends?
The universe has now been rewritten. This entire time there were five among our ranks who were always working for Thanos, but didn’t tip their hand until now. This would be in a way that doesn’t dramatically alter what we have been shown in the past ten or so years of films. Black Widow, Black Panther, Ant-Man, and a couple few others have always been under Thanos’ thrall. There was just never a reason for them to show their hand until now.
Whatever your mind canon wants this to be, keep it. Perhaps Black Widow was always a good guy, and Thanos is manipulating her mind to make her think she owes him. Or perhaps he really has twisted spacetime from a reality we didn’t see to the one we did see. Either way, Black Widow has retroactively always been a sleeper agent of Thanos. She’s always been working for him, gaining the trust of certain people who would eventually be on the battle field of Thanos’ henchmen. What we’ve seen has been a woman biding her time, doing whatever was necessary to get close to Rogers and Stark, awaiting her true master’s directive. The other four as well. They told no one. They were given names of people to befriend is all. How they did it was entirely always up to them. After the final battle (and all or most of the heroes from the past ten years are now dead. We won’t be needing any of them after this), the five heroes turned villains in service of Thanos survive after having slaughtered the rest, and they turn their attention back to Earth. They’ve been instructed to destroy it. They don’t want to, but Thanos has made it clear they only live now because he wills it. He could go back in time just as easily and snuff our their lives by killing their moms before they’re born. He controls them utterly now. They were always meant to lose to the henchmen, who were just supposed to keep the heroes busy while they gained enough knowledge about their foes to pass along to Thanos who could then use that information to go back in time and change reality. The heroes won the battles, but lost the war. They have failed. Utterly. Thanos has won.
The end of Infinity War would be Thanos approaching his love Death expecting her to shine praises on him, as he just tricked these foolish mortals to kill each other and now they’re going to return to Earth and destroy everyone else for him. Only when he visits her she turns on him like a wounded animal. By altering SpaceTime, Thanos inadvertently changed history in ways that gave Mjolnir a heads up Hella was going to destroy it, and when she caused Mjolnir to explode mere months ago, it infected her with a cosmic energy disease. Essentially the essence or spirit of Mjolnir is now inside Hella, slowly killing her. Death is now dying, and if she goes, so goes the universe. That’s where Infinity War ends.
The next film would take place in a dramatically altered Earth without any of the heroes we’ve known, and a universe that’s cracking under the stress of Thanos’ manipulations. All the characters who died at the end of the previous film have now ceased to exist in this reality thanks to the gauntlet, but this is sending shockwaves through spacetime which is causing reality to bend and brake, because generations from now those who died by Thanos’ hand were meant to become beacons of hope and justice that echoed throughout the galaxy, causing others to do good things when they otherwise would have fallen silent. Generations later entire stars were going to be preserved by the actions of people inspired by a small ragtag group of humanoids from a distant planet called Earth. Only now, that never happens, so the future is breaking down. Also actions Thanos made in the past are having repercussions affecting the present. The moon Thanos’ thoughtlessly grabbed and threw at primordial Wakanda belonged to a planet of peaceful people who brought justice and hope to the galaxy: the Nova Corps. Without their moon, the primary species on the home planet of Nova Corps never achieved its greatness, and ceased to be, again sending shockwaves throughout the universe. Paradoxes and temporal distortions and all kinds of fun are just symptoms of the apocalypse. Not just for Earth but for all of spacetime in this reality.
Seemingly tiny alterations of seemingly pointless human lives have repercussions throughout the spacetime continuum. Things that should have happened will not happen now, and things that were never meant to happen do. This causes rips in the fabric of spacetime, that manifest in myriad confusing ways. The entire fabric of reality is coming undone, which threatens to destroy everything, even and especially whatever Death herself holds dear. Earth is like a knot tied to an anchor that was left cemented on a harbor with a ship still attached to it floating out to sea. By trying to appease his lover, Thanos has doomed an entire universe, but these manipulations of time and space have caused other things to happen which Thanos had not taken into account. Hope remains, and new heroes are rising up to take on the battle to preserve the now forever altered universe, and save a mad titan from his own folly. Death and Thanos now have to try to undo the damage to save their own heads, and they turn to unlikely Earthlings to help them do it.
When all this is over, there is no longer one Marvel cinematic universe. Now, each film from here onward is its own universe that may or may not reflect those that came before or after it. This singular MCU splinters into a near infinite number of shards or splinters. Reflections of its former self that are constantly changing and evolving. if continuity errors abound in future films, that’s necessary, and mere evidence of the time Thanos almost destroyed everything.
In other words, if Thanos’ Folly became film canon, it means each film could have an entirely new cast. In the next film’s reality, Tony Stark doesn’t look like Robert Downey Jr. He looks like somebody else. Or maybe he’s a woman in this reality. Whatever the script needs to make a cool movie. Maybe in this movie’s reality, Ant-Man never happened, or maybe Hank Pym happened but Scott Lang didn’t. Or you could do a script about Janet Van Dyne as The Wasp and in this film Ant-Man plays second fiddle to her. The continuity of previous films would not apply to each other. Something like that may have happened but not quite like audiences remember. You could even produce multiple films about the same heroes and produce them within months or years of each other and have them each dramatically contradict each other. Each film takes place in its own alternate universe or ‘shard’ of reality.
Infinity Splinters. The Ultimate No-Prize. You’re welcome.