I couldn't help myself thinking about what it COULD have been, there's a real interesting Dichotomy between Ultron and Vision, two AI's with different views on how to save humankind. I wrote together a rough, possible poor, draft of what I'd liked to see:
Age of Ultron : The Unwhedon version
Intro
The movie starts out as in the movie, with the attack on Struckers castle. Contrary to the movie Hydra only has Scarlet Witch (yes, no quicksilver, one new hero is enough) and she's under the Faustus Device being made to comply. Hydra is also much more powerful and not simply cannon fodder with an arsenal that does real damage against Avengers.As Avengers assault the castle Scarlet Witch unleashes the full force of her hex powers (in my version no mind control stuff only her hex powers), reflecting objects, stopping the momentum of Thor's hammer, setting Hawkeye on fire, manifest "bad luck" effects. After a furious battle she's wounded, defeated and brought in as a prisoner. Stark discovers the scepter and Hydras research into a powerful new AI and brings it back. '
Stark and Banner goes through the AI research and realizes that its key to making their Iron Patriots autonomous. With the threat of enhanced people and Hydra looming they feel a desperate need for reinforcements. Banner argues vehemently against the dangers of an AI while stark tries to ensure that every safe guard will be put in place.
Banner finally seems to convince Stark that's it too dangerous and he agrees to not pursue it. As Banner leaves the room Stark glances down at the computer screen with the integration program, after a solemn moment of introspection he says "I'll either save us or doom us.... lets roll the dice" and pushes the enter key.
The AI takes control, starts modifying an Iron Patriot and self evolves a rapid rate. As in the movie Jarvis intercedes and becomes intermingled with the AI and seemingly defeated.
In a scene they realize Scarlet Witch was brainwashed and manage to break her out of it. They have a conversation and she seems sympathetic to their cause.
Cut to the party scene, except there's no party (that part felt lame) , or Black Widow/Hulk love interest, only the scene with the heroes playing around with the hammer, with Wanda being present.
Black Widow is in the hospital visiting Hawkeye that is recuperating from his wounds.
Ultron does his entrance, contrary to the movie he is in much more of a finished state with the menacing and iconic Ultron "grin". He lays out a logical argument that humanity must be brought under control by AI's to save humanity from themselves and bring peace in our time. The ends will justify the means and a new world order.
He asks Avengers to help him to fulfill their quest. Avengers of course are abhorrent to the idea of humanity becoming slaves under a robot empire and feel no choice but to attack Ultron. A fight between Ultron and avengers ensue, Ultron is soon defeated but as he is he reveals that he anticipated Avengers response and it was a decoy robot. Another sentinel has taken off with the scepter and the arc reactor powering the building has been overridden to go critical. The whole Avengers building and city block is leveled in the explosion. Avengers barely survices by Scarlet witch using her hex powers to create a force field.
Meanwhile a regeneration chamber in Dr. Helen Cho's laboratory whirrs into action. Jarvis has been transformed by contact with Ultron and is replicating a new body.
Avengers retreats to a safe house owned by Shield, a mansion. Sorely in need of enforcements they take a chance and ask Wanda to join them.
Action scene where Ultron raids a vibranium warehouse in Wakanda, easily defeating rigorous security measures. President T'Challa is informed of the raid and contacts the Avengers.
Ultron begins his assault to bring humanity under his heel, infiltrating the internet, bringing down Wall Street, shutting down the grid. Ultron puts an ultimatum to Hydra, obey or be destroyed. Hydra complies and agrees to put its resources to Ultrons disposal.
Hawkeye and Black Widow having been separated from Avengers roams the street to reconnect with the Avengers, protect citizens and eliminate Hydra Agents.
Middle Act
Avengers get an emergency call that Ultrons sentinels are assaulting a Shield laboratory using the information it has gleaned from Avengers databases). The warehouse is a stockpile of gamma bombs. Avengers has no choice but try to prevent them falling into Ultron hands. In the ensuing battle Avengers are almost decimated, the Ultron sentinels are resistant to almost anything due to their new Vibranium bodies and hive mind. In a last ditch effort hulk holds them off while Avengers retreats, having set the gamma bombs to detonate. The Avengers barely escapes and Hulks lifeless body is found in the rubble.
Hulk is put in a regenerating chamber, seemingly being a coma. Stark is battling his feelings of guilt from creating Ultron. Suddenly signs appears that something seems to be fighting Ultron, putting the grid back online and putting Wall street back in order. Banner asks "who?". A figure steps out of the shadows, it's Vision who replies "me".
Vision tries to explain his purpose and desire to help, but the team is distrustful of another AI, with nerves short they attack Vision. He uses his powers to phase through the attacks. Vision sees only one way to prove that he's benevolent. The battle suddently stops when Vision phases through Thor, grabs his Hammer and raises it over his head to the dumbfoundness of the Avengers.
Vision explains that he believes Ultrons ultimate plan is to keep them occupied until he's been able to re-purpose the soul stone from the scepter to integrate it with his metal body. With its power and mind control capabilities he will be unstoppable. They must attack launch an attack on his fortress in Sorokovia immediately.
Finale
Avengers and all renaming Helicarriers begin their final assault on Sorokovia, Ultron's sentinels are more powerful than ever and the whole castle is protected by a powerful force field (probably better now than in beginning due to escalation). With Vision and Scarlet Witch they barely manage to keep them at bay. After a hard fight the Avengers fall victim to Ultrons now superior powers, intelligence and strategy. Only Vision is left conscious and the others are in Vibranium Shackles. Vision and Ultron has a philosophical discussion about saving humanity each laying out their argument for each. Unable to come to consensus program indicates the soul stone is ready for integration.
Ultron goes toward it, all is lost. Ultron stops and look at the growing shadow on the ground and up ... as Hulk smashes into him, gamma can't kill Hulk, Hulk is gamma! Hulk bashes Ultron relentlessly but the Vibraniun doesn't yield. Ultron prevails, lifts Hulk into a choke hold and starts blasting him into whimpering disintegration. Vision crawls towards the soul stone.
As he's about to kill Hulk he says "So this is how earths mightiest heroes end, not with a bang but with a whimper". You hear Vision behind him saying "No... this is where it begins" Vision now fully restored by the soul stone blasts Ultron, as he disintegrate his last words are "Peace... in ... our ... time"