As you know if you've seen the movie, Agent Coulson suffered a pretty grievous wound and apparently died.

But I've seen it speculated elsewhere online that while he seemed to die and Fury told others he died, we also saw Fury outright lie about the cards being on him, knowing what Coulson said about the Avengers needing his death was true.

But what if Coulson doesn't stay dead? You have to figure they've got some nice med tech on the Hellicarrier, and some fans online have presented the idea that they make Agent Coulson the classic Avenger "Vision" for Avengers 2.

I didn't know much about the android, but a quick check of wikipedia shows that he's based on tech indirectly from Pym/Ant Man, and what movie is currently in pre-production still? Ant Man.

So depending how they take Ant Man, imagine a plot set before Avengers. Ant Man's plot sets up the character of Ant Man, and probably Wasp and others, but then the movie ends in such a way to explain why they miss the action of Avengers, even if it's just walking away from their responsibilities. (The events described below will be a good way to draw Pym back in Avengers 2.) (Maybe throw in a mention in Iron Man 3 why War Machine missed out, while you're at it).

But after the credits, you flash forward to the Hellicarrier, undergoing repairs after Loki's escape. We see lab equipment we just saw used by Ant Man during the movie, and we see a med team rushing in a gurney with a body under a sheet. They're switching on equipment, and Fury perhaps comes in. He walks over to the table and says something like, "We're not quite done with you yet, Agent." The sheet is pulled back and it's Coulson.

Then you can play it up a bit more in whatever other Marvel movies you do leading up to Avengers 2, alluding to Fury being preoccupied with a new experiment. Perhaps you even have him appear in uniform in Iron Man 3, maybe even gone rogue somehow (like the shadowy council taking him away from Fury because of how he disobeyed in Avengers). Or you could end Iron Man 3 with Stark casually looking at the info he stole from the Hellicarrier computer, like maybe Jarvis alerts him that he found something interesting that is further encrypted. End Iron Man 3 with Stark looking utterly shocked as he looks at the screen, or just saying "Interesting" because he sees information about an android, "Project Vision" (but nothing about Coulson.

Or if you make it a larger part of Iron Man 3 or one of the other movies, like a Shield/Fury movie, Stark has to ultimately take him down/reprogram him. Then you can bring Vision back to save the day at some crucial point in Avengers 2.

It'd also bring up doubt again about what Shield is keeping from them, how Fury is toying with their emotions, and also the ethics of turning Coulson, a man with his own life and death, into a tool. The usual "am I a man" questions. Stark could become consumed by it, even, being a cyborg himself.

Yes, some will see it as cheap to un-kill someone, but this is Marvel, and in the comics, nobody stays dead forever. Most importantly, Gregg had great chemistry with so much of the cast and it'd be great to see him come back in a bigger way.