Right now, as it is, there is no information regarding the Metal Gear Solid movie. As a fan of the series from Metal Gear Solid and onward, I want to see this movie made. I want (rumored) Jordan Vogt-Roberts to do this well.
Hideo Kojima is one of the writers listed on the IMDb webpage, however, I am not sure if that means the movie will be based on the video game, or if Hideo Kojima is contributing to writing a new story.
MERYL - Scarlett Johansson
Meryl was one of my earliest crushes when I was younger playing the game. Johansson would fit well in this role, Meryl was a bad ass chick. A little nervous at first, but then she got her cool. The movie could show what she was doing while Snake was out in mission. Johansson could pull this off.
TO DO IT: The only thing about the movie is the writers would have to make Meryl less a damsel in distress and more bad ass. In other words, they would need to tailor the character more to the actress.
BIG BOSS - Michael Biehn
The man from Terminator who was John Connor's father. The man was in Aliens, The Abyss, Tombstone. This man is no newcomer to action movies and you need someone as seasoned to play Big Boss.
TO DO IT: He just needs the eye patch, grow the beard out and just do it.
OCELOT - Michael Rooker
The Walking Dead and Guardians of the Galaxy. That's where you've more recently seen him. In the Walking Dead he played Merle and in Guardians, he played Yandu, paternal figure to Starlord.
TO DO IT: Give him two guns and a mustache and grow his hair out.
SOLID SNAKE - Hugh Jackman
Come on. Let's get real. There is no one else in the world who has time and time again proven to be a real bad ass. This man has done it all, even Theater. Jackman is my pick for Solid Snake, though he doesn't have the voice of Snake, he should does have the ability to play him. He could mix some of his Wolverine-esque animalistic persona with his role in any other movie. He is ripped enough, and if Christian Bale can change his voice for Batman, I'm sure Jackman could work something out.
TO DO IT: He would need to do almost nothing. He could really pull this one off. I mean stranger things have happened.