Deadpool's writers like the idea of Arnold for Cable:

Interviewer: So it definitely looks like you’ll have a lot of sequels — I’m rooting for Arnold Schwarzenegger to play Cable, personally.

Rhett Reese: Oh my God, that’s such a great idea! He’s got the exact right hair, too, the flattop!

Interviewer: And he’s got that sense of humor, and of playing the straightman — but also to be funny — to Deadpool’s clowning around. I’d love to see that.

Paul Wernick: I like that idea.

Info: http://www.forbes.com/sites/markhugh.../#3f5dcdf95407