My ideas on casting:
Too bad Philip Seymour Hoffman is no longer around. That man was a great and versatile actor, he would have been a great Steve. R.I.P. So, perhaps:
Steve - Denzel Washington: Denzel Washington strikes me as an authoritative leader, and his roles as a leader have him always being the guy to get shit done. He's also familiar with the passive aggressiveness and sharp wit that characterizes Steve.
The Doctor - Dr. Steel: The man's got a musical and acting background, though of a more wacky demeanor than what's found in the ER-verse. Still, he does bare a striking resemblance, and I like that he doesn't have the typical lanky/thin build for a mad-doctor, but a muscular tough one, which would be more appropriate for demonstrating The Doctor's raw power.
The Armory Master - Scarlett Johansson: She's has a demeanor of someone older and more experienced in her actor, while still retaining her beauty and grace. Her hair would need to be shortened and dyed for her role, which she has done before like in 'Under the Skin'.
Coincidentially, one of her upcoming films looks like it might as well be about the Armory Master's origins anyways.Nyars - Javier Bardem: I've always thought Nyars was thug-like in his behavior, but not in the "I'm a tough-guy and I'll fight you rawrrawr"; he's more of a practical pusher man. I also feel like he should have some sort of accent, and so to combine these two factors, I'd choose Javier for roles he's played in the past, where he's all about shady business, and has an excellent grasp of the English language even with his accent bleeding through.
Milno - Some Young Dude: Fuck, this is a hard one because of Milno's age. Bionically, I'm guessing he's in his early 20's, and I was coming up with all sorts of options until I realized that they've all suddenly become old guys. Mark Whalburg, Chris Evans, Will Smith, Ed Norton, etc. They were all in their 20's, and then 5 years later, they're suddenly middle-aged. How does that work? I wouldn't want to try it, and have it end up like Leonardo Dicaprio in "The Great Gatsby", where he tries to pass off for 29.
Faith - Natalie Portman: She looks just like a Faith-type, maybe she'd need to add some Red to her hair. Plus, as of late, a lot of Natalie's movies have her losing her sanity and going nuts, much like Faith on occasion.
Feyri - Rooney Mara: I've thought of Feyri as the tall, slim, rational, maternal "team mom" to keep everything in order, like Rooney, who isn't afraid to resort to the ultraviolence when necessary either, even if she has some moral hang-ups.
Lyra - Yuko Goto: Yuko plays cute, nervous, mousey girls all the time. And what is Lyra? Well, she's more "catty" than mousey now, but still.
Stacy - Stamper: Okay, Stamper's a Youtube Personality, but since this is all hypothetical fun, we should be allowed to make stretches. Besides their age difference, I've always used Stamper's appearance and personality to imagine what Stacy would look and sound like.
Stamper's "Potato Salad" illustrates what I believe a normal day would be like for Stacy pre-HMRC. (WARNING: Crazy Bullshit.)Elizas - Pharrell Williams: For a long time, I thought Elizas would be more like Jamie Foxx or Kanye West. As of now however, the former is to old to play Elizas, and Kanye is sort of...Kanye. Pharrel is almost as old as Jamie Foxx, but he's been taken youth elixir or something. Seriously, how is he 40? He also looks like he could play a guy trying to get with all the ladies.
May - Katy Perry: Honestly, I really like this one. Look at the similarities: They both constantly switch back and forth in their personalities between a sweet, innocent debutante, and a terrifying crazy succubus. People are split on whether they're cute girls or spawned monstrosities. Both do wack, crazy shit, all the time. And they're both fair-skinned, dark-haired, big-eyed women with ample assets. Hell, I was just looking at some music videos, and not only could Katy Perry play May, it works vice-versa: any of Katy's music videos could easily be explained as something created from May's mind/perspective.
That's all I got for now, maybe I'll think of some more later.