It's easy to use Ironman, Captain America, and the other Avengers since they've become household names since their movie franchises have become popular. The problem with this is a lot of interesting characters get left out in the cold and not used for bigger and better things. That's not to say that every character deserves a movie, but there are other ways to use characters with potential.

Fantomex:

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Everyone loves Gambit because of his smooth talking and charming personality. That combined with his slick moves and destructive powers make him extremely likable. There is a fairly new character who has all of Gambit's skills, smoother, tougher, and a much better fighter. That man is Fantomex. On top of the skills that were mentioned, Fantomex is a more disciplined and "sophisticated" thief than Gambit will ever be. In Fantomex's first few appearances it was unclear on whether Fantomex was a hero or a mercenary out for himself. Years later, it's still unclear.

While Fantomex has done more than a few things that have redeemed him for some of his past sins, he continues to do things that make you question his motives. For example, he shot a kid in the head and killed him so he wouldn't grow up to become Apocalypse, but then cloned him and raised him to be a better person so he would grow up and become a better person. He will tell everyone how much better he is than everyone, then admit he likes and needs his teammates. Fantomex will lie, rob, and manipulate, and then turn around and sacrifice his life for someone he loves. Like all great characters, Fantomex isn't a one dimensional character and it's shocking how more people don't know about him.

Fantomex is one of the few random characters that would make a good solo movie. Like Wolverine, Fantomex is a product of a clandestine government agency that was using mutants to do their dirty work. His story isn't as tragic as Wolverine, but it's a good story to tell nonetheless. But like Deadpool, Fantomex would need some momentum from the comics and the help of internet memes to make him a household name. If FOX is really going to put on an X-Men show, Fantomex would be a great person to have on as a regular.

Sergeant Cole Alves:

The Punisher is one of those characters who works alone because he feels he can't depend on people when the chips are down. Then Frank Castle met former U.S. Marine Sgt. Rachel Cole-Alves. A former woman who lost everything she had on the day of her wedding. During her wedding reception, a group of gangster openned fire and attempted to kill everyone. Rachel Cole-Alves who was left in critical condition. After she finished rehabbing after the massacre at her wedding reception, Cole-Alves eventually comes across the Punisher who agrees to work to work with her since they were both after the same people. Maybe The Punisher felt a connection to her after finding out how she lost her family simiar to the way he lost his.

Regardless of the reasons for Castle letting her help him, she worked with Castle closely, he taught her how to do what he does the right way, and she even dawned the Punisher skull shirt like he did. When Alves-Cole was arrested, Punisher sacrificed his freedom to give her enough time to escape prison and the death penalty. Alves-Cole ended up in Detroit where it looks like she continued Punisher's work while he was being kept under lock and key in an underwater prison designed by Tony Stark.

This image alone should sell you on why The Punisher took her under his wing.
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It seems like the new trend is to make older male characters and turn them into women. The new Wolverine is X-23, Blade's daughter is going to be the new Blade, and so on. While it would be a better idea to make new characters for women instead of rehashing old ones, this particular one makes a ton of sense. Some comic book writers have written that the Punisher does what he does because of a deal he made with a deity or a demon. Either way, eventually the Punisher was going to get too old to punish or die and someone new would have to be appointed to carry out for that particular supernatural entity.

It would make sense that the way things were set in motion would be something that would be the same as Castle's. It was weird that Marvel isn't making her a thing. She could be a very popular character to use especially since Frank Castle is realistically over sixty years old (now he looks like he's in his thirties or forties for some weird reason). Either way, the ball was dropped with Cole-Alves. She could have been special.

Dark Beast:

This Beast even has a darker coat of fur. And yes, that is blood on his claw.
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Of all of the The X-Men's, Hank McCoy (Beast) is probably the most gentle person on the main roster. Despite his outer appearance, he's more Reed Richards than a beast. He enjoys not having to fight and his teammates love him because of the giant heart he has. Now, his Age of Apocalypse counter is the antithesis of everything Hank McCOy stands for. This Hank McCoy is what happens when Apocalypse gets to him before Professor Xavier could. Dark Beast enjoys torturing people during his experiments and has even experimented on himself so many times that it lead to his inevitable death. Dark Beast is just as bad as Mr. Sinister is. Actually, Dark Beast is worse.

At least Sinister believes in something while the Dark Beast just does things for the heck of it. There is no real reason. He's just a horrible person and he embraces it.Dark Beast's character won't work as a solo act. So where do you put him? He would make an amazing nemesis. He's brilliant, disgustingly unethical, and can hold his own in a fight (strong, agile, and likes hurting people). While it won't happen, FOX could make their current Hank McCoy and make him a bad guy easily. He already feels like an outcast regardless of being in his human form or in the blue fur, so him meeting Mr. Sinister or Apocalypse and turning him evil isn't a stretch.