I would be much more worried about the writing than the casting. I could just see a situation where they make a rough cut that's really true to the tone of the game, but then test audiences don't like it, so producers take a hatchet to the entire thing and bring in Joss Whedon to "punch it up" and we get a flashback scene with The Deserter where a coalition airship comes over the horizon and he turns to his fellow revolutionary and says "they fly now!?"