I would still take Manziel and hope that he could correct his desire for preparation, showing up on time, and not partying. I wouldn't be extremely hopeful, of course, but I'd take the chance. I view him as a good "buy low" candidate.
Or put another way, if the question is would I rather take a chance on one of the second-tier 2015 QBs or Manziel, I'd take Manziel. EJ or Manziel, I'd take Manziel.