So, when reading Steelheart, why did this never occur to anyone:
Hugh Jackman as Steelheart. In the book, Steelheart is described as huge, and there's a pun waiting there somewhere. I think Jason Momoa or Chris Hemsworth could work though.
For Prof, I always pictured him as Jack Nicholson, or maybe Viggo Mortenson. Not sure why I thought of Aragorn, but in LoTR, Viggo managed to be both quiet and calm with an undercurrent of intensity, and then just plain intense when needed, like Prof.
As Tia, I fully agree with Gina Torres, but maybe Gillian Anderson, because Scully.
Ron Perlman is the only one for Cody in my mind.
For Abraham, I think Tom Hardy could pull it off, or Idris Elba. (Didn't someone already say that?)
Megan, I think, would probably be Chloe Grace Mortez. She's already a good actress for being so young (If I remember correctly, she's seventeen, which makes her close to how old Megan looks.)
Then for David, it would probably be an unknown, but I always pictured him as Brenton Thwaites. I loved Thwaites in The Giver, and I think he'd be fantastic here. Andrew Garfield could work.
The Babilar Reckoners, besides Val, I don't know. As Val, I kept thinking Halle Berry.
The Epics:
Hugh Jackman as Steelheart.
Ken Wantabe as Nightwielder.
For Conflux, Newton, Fortuity, and Regalia, I dunno.
Again, Deathpoint draws a blank. I pictured him as Robert Carlyle, but I'm not sure if that'd work.
And as Obliteration, Vin Diesel. Full stop.
But first, the movie actually has to enter this stage. I believe Brandon sold the rights or something, but I'm not getting my hopes up.