Should:
1. The Mandarin
Jon Favreau decided to pass on iron man's top rival in the first two movies, and with this most likely the iron's final outing, the Mandarin is a must. Using this villian is also a good idea because a lot of people could not stand the fact that that the first two villians were non-superhuman.
How he should fit into the storyline:
The Mandarin should be out to get Tony because he possesses the last makulan ring without realizing it. To help steal it, the Mandarin hires henchman Donald Gill (a.k.a the Blizzard). The. Mandarin should exist throughout the movie, but only make first contact with iron man until there is about 30 minutes left. In case you didn't pick it up, he should be the main villian.
Who do you think should play the Mandarin?
2. The Blizzard
I believe that for iron man to make a comeback, the movie needs to have more than one big villian for iron man to take down. This, I feel could make it apparent again that iron man is such a kick-butt hero and doesn't need teamwork to defeat a villian (like in the Avengers and Iron Man 2, more emphasis on this later). I think Blizzard would be a good fit for this roll because he is a big force to be reckoned with, but not that big of a force.
How he should fit into the storyline:
Blizzard should have been originally hired by A.I.M to steal vibranium from countries that have some of it so they can use it for weapons. But Blizzard is stumped by iron man and a friend ( not yet mentioned by myself). After this the Blizzard is lost track of until the Mandarin seeks him out.
3. A.I.M/ M.O.D.O.K
There is just something about this idea that I just can't get enough of. To me the action that this group of antagonists can bring to the big screen. I could picture iron man and friend (again) in the air in NYC battling A.I.M around Stark Tower. I could picture iron man and friend stopping them from attacking Stark headquarters in California. The only problem I see with this is what in the world would MODOK look like?
How they should fit into the storyline:
As mentioned before, AIM goes out and hires Donald Gill so he can go and collect vibranium. After iron man and friend stop Blizzard, he reveals that AIM had hired him. After AIM goes under full beatdown in some heavy battles, they decide to build MODOK so they will not be beaten so badly in case this happens again. But, MODOC goes on overdrive and AIM must seek iron man out to help destroy "him" (?). Afterward, AIM is taken in by SHEILD.
4. Black Panther
This is the friend I kept mentioning. This is what will lead Black Panther into The Avengers: Reassemble (?). I know this sounds just like Iron Man 2 and that your probably thinking: but weren't you just saying that it shouldjust be iron man? Yes, I did but I have a solution for this.
How he should fit in:
Black Panther finds that Blizzard has stolen vibrainium from his country and he declares vengence against Blizzard as the Black Panther. After looking, he finds that Blizzard is in North Korea to steal the precious.metal. As it turns out, Stark is also there giving peace speaches. Iron man sniffs something out and then ends up helping black panther in battle with Blizzard in the mark 5 2.0. When the battle is over there is almost immediate connection between the two and they agree to help each other when needed. Black Panther figures that AIM is Behined this and goes in pursuit of them. Again, iron man comes to help and AIM is defeated. This is the last we see of him, so this means that it is just iron man in the final battle.
5. Final battle just Iron Man
As mentioned before, iron man needs to do this himself. I have an idea how this may work.
How this should work:
Iron man seeks help from war machine to defeat MODOC. But in the battle war machine gets injured so iron man only has himself to defeat the Mandarin and Blizzard.
The following shouldn't happen for either obvious reasons or it was somewhat mentioned before.
Titanium Man/ other metal villians
Major SHEILD involvement
Drinking sub-conflict
NO SENATOR STERN
NO HAPPY HOGAN- Jon Favreau ruinined the direction of Iron Man 2- don't let him back!
Fing Fang Foom- the levitahn in the Avengers
Iron Man 2 Howard Stark, Captain America Howard Stark made to look older
Stark/ Potts wedding
Black Panther Casting Article: http://www.comicbookmovie.com/fansites/theavengersassembledinfo/news/?a=53343
If the Iron Man 3 movie is like what I had just wrote, it might just be better than the original.
I also like the idea of The Mandarin revealing himself as the "puppet master" in the first two films (ten rings group, Vanko mentioning ten rings group)