You know who'd be good as Reacher? Liam Neeson, 15 years ago. Or just rewrite the character as older. (why not, they rewrote him shorter)
If you've seen him in Taken and The Grey, you know what I mean. Trivia: Neeson was an amateur boxer before he became an actor. He's not real muscular, but he has the physicality and plenty of acting chops.