I think Shogun's gonna be your biggest problem casting-wise. Who the fuck is gonna be able to pull off being an arrogant, cocky cunt one minute, then turn around and be some frightened paranoid fool the next (and actually make it LEGIT ?)
Revolver's character can be played by most (in spite of any "perfect castings" you have), but Shogun's defo gonna be difficult. Likewise with Rev's handler. Don't let her be a smokin hottie with glasses, she's gotta be ugly, coz in Rev's situation, you'd have to do a lot of explainin as to why he doesn't just bang the shit out of her.
I'm gonna have to get Christoph Waltz to play Shogun. That motherfucka can play anyone.
In all seriousness, i'm gonna need to change Shogun a bit more cause he's too similar to Revolver anyway. And being a complete paranoid bastard from the start would kill some of the tension (seriously where's the threat in a guy who constantly shit his pants?) I'm thinking of integrating more of his paranoid nature in his opening dialogue so it would make sense he'd go full blown paranoid in the next scene to motivate Revolver to stop fucking around, then regress back to being determined to kill Revolver. But even in the beginning, he still needs to be imposing. It's a real delicate balance. I'm sure I can find an actor who can pull that off.
As for Angel, the best I can do is make her "plain" cause no actress is gonna want to play an ugly girl, let's be honest here. Unless they're looking to get an Oscar which there is no chance with this movie. No studio exec would want that either cause sex appeal sells. But now that i'm integrating her more, the pressure will probably be to make her the love interest. I'm completely against forced romance but if I have to make it happen, then it has to be convincing.