Even if the mental side clicks eventually, I'm not sure his arm talent will allow him to succeed.
JH had/has arm talent. He wasn't as accurate as Tua but who is? But once he started to understand coverages, footwork and timing, he started to succeed, even at Bama, OU and obviously now in the NFL.
JM? Probably the most inaccurate QB at Bama I can ever recall. Even on a long throw, which is his supposed strength, he was often very inaccurate. And in short to medium range throws, he was terribly inaccurate and showed very little ability to throw passes in tight windows, the way a successful NFL QB must do to move the chains on 3rd downs.