Story Outline:
Part I:
1. Each member of the avengers is seperately attacked by a different villain. Iron Man by Justin Hammer, Hulk by Abomination, Captain America by Baron Zemo, Thor by the Executioner, Hawkeye by the Swordsman(his former teacher), and Black Widow by Red guardian(her former husband and kind of a Russian captain America)
2. At the same time SHIELD is attacked and the numerous supervillain prisons have are broken into and many different c/d-list Marvel villains are unleashed. At the same time Scott Lang, Ant-man is working with SHIELD to create an army of robots(Ultron) for combat using some tasseract weapon technology they have left over.
3. Thanos breaks into Odin's vault in asgard and steals the Infinity Gauntlet. He also rescues Loki from his imprisonment.
Part II:
1. The Avengers all defeat there respective foes and then learn of the prisoner escape. They go to help SHIELD and their army of Ultrons round-up the criminals. We first see Ant-man in action as he helps.
2. The newly regrouped masters of Evil, now led by Mandarin, attack the avengers again and as they are defeated Mandarin reveals that Thanos is coming.
3. The Avengers assemble(maybe with Falcon and war machine) and Fury reveals that SHIELD knows about Thanos and the infinity gauntlet.
Part III:
1. Thanos arrives on Earth along with an army of Chitauri. The army spreads out around the world in search of the six Infinity Gems.
2. The Avengers and SHIELD agents split up into teams to go after the respective gems. Captain America and Falcon go to Wakanda(I think in Captain America 2 this will also where he will go), Iron Man and War Machine go to Egypt, Nick Fury and Maria Hill go to Paris, Thor and SHIELD agent Bobbi Morse(mockingbird) go to Norway, Ant-man and Hulk go to Greece, and Hawkeye and Black Widow go to Moscow(or perhaps Morse and Hawkeye will team up given their history in the comics), If Wasp is in the movie then the team-ups will be a little different
3. Each of the respective teams (along with some Ultron robots) fight, but are defeated and the Chitauri gain all six of the gems. Perhaps in Wakanda, T'Chaka, the current king is killed, setting the stage for his son T'Challa to become king and eventually join the avengers as Black Panther
Part III:
1. Thanos retrieve all the gems and attempts to use the Infinity Gauntlet. The Avengers regroup and defeat him.
2. The team recoups after their victory and Tony reveals the new Stark tower where they will all live
Tag: At the end with see Ultron becoming self-aware, setting him up as the villain for Avengers 3.
There are some of my ideas for Avengers 2. Tell me what you think and what you want to see in Avengers 2.