While Kreuk plays Chun-Li, Duncan will take on the role of Balrog, Yune, is the mystical Gen, and Klein will be Nash. As it breaks down in the game... Balrog* is M. Bison in Japan, and Vega outside. Since we're talking Duncan, that means M. Bison/Balrog -- a dude who holds a lot of similarities to a certain ear-biter. (This re-naming is ridiculous...) Gen, meanwhile, is an old, master assassin and friend of Chun-Li's father, who blames himself for the violent path the girl followed. And lastly, Klein's Nash -- also known as Charlie. This guy is a first lieutenant in the US Air Force who died in earlier games, but shows up in later ones, and is a friend of Guile.
I guess if Ryan Reynolds can take on Blade, anything is possible. But every time I try to think of Klein in this role, I hear him in his do-gooder voice saying: "Dear God, thank you for all your blessings. You've given me so many things, like good health, nice parents, a nice truck, and what I'm told is a large penis, and I'm very grateful, but I sure am worried about Tammy." And we can't forget -- Klein headed Rollerball.
*Post Edited: Variety says Bison, the villain, is still being cast, presumably that's this Bison/Vega. Stay tuned for more name confusion!