2. Iron Man: The Crossing
Premise: It turns out that Iron Man isn't the good guy we all thought he was; he's been a sleeper agent the whole time, working for Kang the Conqueror. When The Avengers get wind of this, they travel through time to bring a teenage Tony Stark from an alternate timeline into the fold, who steals an Iron Man suit and eventually manages to convince present Tony that what he's doing is wrong.
Why It Wouldn't Work As A Movie: Ambitious and somewhat clever, there's still no way it would fit in with the current tone or narrative arc of the Marvel Cinematic Universe's Phase Two. Furthermore, unless you really know what you're doing, introducing time travel into the mix can be a poison pill for these sorts of franchises, and given how complex the narrative web already is, it's not recommended to throw something so challenging in there. Also, there's the fundamental issue that Iron Man is everyone's favourite character from the Avengers roster; turning him bad even temporarily and using that to sell a film is a horrible idea.
Chance Of It Happening: 0/10