CABLE
I usually don't get amped about actors playing any particular roles but holy *beep* Stephen Lang would be *beep* perfect for the role of Cable.
I grew up reading X-Men comics and Cable was one of my favorite characters back in the day.
As soon as I heard Cable is to be featured in the sequel to Deadpool, I immediately envisioned the scene from Avatar when the antagonist colonel quickly pats out the fire on his shoulder as if it's only a nuisance. That scene completely embodies the disposition I would expect from the Cable I grew up with.
As I said, I didn't even know who Stephen Lang was by name, but I knew the actor who played that bad ass marine colonel from Avatar is the only person I can think off that can pull it off perfectly.