S.W.O.R.D. wants to reacquire Vision and continue their agenda to safeguard the world against another Thanos.
S.W.O.R.D. - Sentient Weapon Observation and Response Division - was founded by Maria Rambeau (Lashana Lynch), although it's not clear yet when exactly after the events of S.W.O.R.D. to the MCU.
Of course, Vision (and Scarlet Witch) died during the Battle of Wakanda in Avengers: Infinity War when Thanos removed the Mind Stone from his forehead, killing the synthezoid. There was a five-year gap after Infinity War and the main story of Avengers: Endgame where the world had to carry on despite the absence of half of its population, and the Avengers' time heists of the Infinity Stones in order to resurrect the lives Thanos took proved successful. Meanwhile, the Thanos of 2014 used the Quantum Realm to arrive in the MCU's present-day of 2023 in order to conquer the Earth. All of Earth's defenders assembled alongside the Avengers to beat back Thanos' army, but the Mad Titan's invasion was brief yet devastating. Thanos' starship destroyed Avengers Compound with missiles and it took Iron Man (Robert Downey Jr.) sacrificing his life by using the Infinity Gauntlet to end Thanos once and for all.
WandaVision takes place only three weeks after the Blip in Avengers: Endgame brought the billions of souls Thanos killed with the Infinity Gauntlet back to life. Fans found out via Captain Monica Rambeau (Teyonah Parris), Maria's daughter who was resurrected by the Blip, all about S.W.O.R.D.'s current activities as the agency has now taken charge of Earth's defense against future alien invasions, and they had possession of Vision's corpse. Taking the organization's name literally, S.W.O.R.D. was revealed to be developing sentient weapons and it has to be because of the fear of another Thanos.
Endgame Changed How The MCU Handles Alien Threats
Prior to Avengers: Endgame, the MCU's response to alien attacks was fielded by Nick Fury and S.H.I.E.L.D. Fury concocted the Avengers Initiative after meeting Captain Marvel (Brie Larson) in 1995 but it wasn't until Tony Stark's debut as Iron Man that Fury actively began recruiting for the Avengers. The arrival of Thor (Chris Hemsworth) in New Mexico, where he and his Asgardian friends fought the Destroyer, created an urgency in Fury to form the Avengers, which was exacerbated by Loki (Tom Hiddleston) invading a S.H.I.E.L.D. facility and stealing the Tesseract, which was the Space Infinity Stone.
In Fury's own words, the idea behind the Avengers was to have a superhuman response team "to fight the battles we never could", referring to both superpowered villains and aliens like Loki and the Chitauri. Fury even told the World Security Council as such after Captain America: Civil War.
It's clear that after Thanos Snapped half of all life in the universe out of existence in Infinity War and then returned to finish the job in Endgame that Earth needed a more organized and powerful military response beyond relying primarily on the Avengers, especially since the status of the Avengers as a team is questionable after their ultimate victory in Endgame. S.W.O.R.D.'s retcon as having existed for an unspecified amount of years is the MCU addressing the necessity of having a specialized agency that deals with extraterrestrials. (Although, in WandaVision, S.W.O.R.D. seems to function much like S.H.I.E.L.D. did since Wanda Maximoff isn't an alien menace.)
Did SWORD Plan To Create Sentient Weapons From Vision's Corpse?
WandaVision revealed that at some point in between Avengers: Infinity War and Avengers: Endgame, S.W.O.R.D. acquired Vision's corpse from Wakanda. How this was accomplished isn't clear but Vision's technology became S.W.O.R.D.'s property, a fact that Wanda Maximoff discovered soon after she attended Tony Stark's funeral in Endgame. Wanda then attacked S.W.O.R.D. Headquarters and stole Vision's corpse before absconding to Westview and creating her TV sitcom fantasy world inside The Hex, which magically sealed off Westview, New Jersey from the rest of the world.
S.W.O.R.D.'s Acting Director, Tyler Hayward (Josh Stamberg) told Monica Rambeau that in the five years she was dead, the agency shifted away from manned space missions to "robotics, nanotech, A.I. - sentient weapons like it says on the door." Obviously, the most advanced A.I. machine in existence was Vision so S.W.O.R.D. needed his remains to further their revised agenda of protecting the planet from new alien threats. Some fans even speculate that S.W.O.R.D.'s "sentient weapons" could turn out to be Sentinels, the dangerous mutant-hunting robots that will become a menace to the X-Men when they finally debut in the MCU. Regardless, Vision was part of a top-secret project codenamed "Cataract" that Dr. Darcy Lewis (Kat Dennings) unlocked in S.W.O.R.D. and Hayward's encrypted files. It stands to reason S.W.O.R.D. wants to create a new legion of sentient Visions as weapons against the next Thanos.
How WandaVision Changes SWORD's Plan
Wanda Maximoff was the proverbial monkey wrench in S.W.O.R.D.'s plans and Tyler Hayward redirected his agency to deal with Scarlet Witch. Whereas S.W.O.R.D. sees Vision as stolen technology and property, Wanda has a very different view of Vision: He's the love of her life and she made Vision her husband in her fantasy within the Shangri-La of Westview. It's also become clear that Vision can't live outside of the Hex and without Wanda's magic; curiously, Vision doesn't have his memories of who he is and who the Avengers are even within the Hex.
However WandaVision ultimately ends, it's unclear how S.W.O.R.D.'s original plans for Vision can go forward if Wanda Maximoff is protecting Vision from them. And yet, Earth would likely benefit from S.W.O.R.D.'s sentient weapons as a line of defense against aliens, so Wanda's desires could very well be endangering the planet in the big picture. No one in the MCU will ever forget what Thanos did and the facts are there will be more aliens coming to Earth (or already arrived) who will have similar ambitions to destroy humanity. Thanos permanently changed the MCU in Avengers: Endgame and now S.W.O.R.D. is picking up the pieces by developing weapons beyond the Avengers - but time will tell if they will get Vision's corpse back to complete their mission when WandaVision is over.
