Many of us have recently seen the superb new superhero movie, X-Men: First Class. Although I will spoil the ending as little as possible, one can say that it is set up perfectly for the sequel. But for the next movie, I would not have a simple clash between the newly formed Brotherhood and X-men. Instead, I would have a more complex plot. Here is my idea: Xavier and his team start off in the movie unaware of the Brotherhood's movements and actions. But a new threat to them has formed to them: xenophobic Bolivar Trask and his Sentinels. The government's new mutant hunting-policy drives many mutants into the arms of the Brotherhood. In a three way battle between the huge Brotherhood, the X-men, and the Sentinels, Bolivar Trask is killed. Without Trask, the Sentinels quickly turn on humans, seeing the need to establish order, just as in the comics. To protect the humans, a new, powerful recruit (mentioned by Vaughn in interviews) joins the X-Men. After destroying all the Sentinels, The Brotherhood and the X-Men have an epic battle. The movie finishes by showing previously unknown Master Mold.
Here are my ideas for the recruit, based on Vaughn's comments (they are powerful enough to go toe-to-toe with Magneto):
Cable
He is a fairly obvious choice, as the producers have said it would be great to have him in the movie, although his backstory would need to be significantly changed.
Best Played By: Stephen Lang
Multiple Man
Think about it: It could be a great showdown between Magneto and him, with Magneto killing hims (?) as fast as he can make them.
Best Played By: James Franco (really had trouble on this one. Suggestions are more than welcome)
Hellion
My top choice. Just imagine Magneto and him mentally throwing giant objects at each other. The green fire would definitely help differentiate who controlled what as well.
Best Played By: Aaron Johnson
That's all, folks! Questions, comments, insults? Sound off in the usual place.