I cover most of it ITT:
But let's go over the cliffs of it:
1. He's NEVER had a full off-season
2. Now he'll not only have that full off-season, but he'll be getting the first team reps
3. His closest physical parallel and former HoF'er: Elway himself has pledged to be working with him (for details there are several articles. More importantly ones where Elway debunks your throwing motion criticism and says they'll be working on footwork to develop the consistency he needs)
4. He'll finally have a real system. Not to criticize what they developed for him on the fly... but it was on the fly. Now they'll have a foundation to build off of and the mental game can be formed instead of a primary focus on athletic reaction.
5. One of, if not THE, best work ethics in the business.
6. It's already shown MASSIVE improvement. Reference an ESPN special in December where they highlighted his footwork improvements. Reference every quote from Elway to Mariucci to Brady and Belichick and the Pat's QB coach, etc
So in summary:
He's already shown huge improvement. Now we get the opportunity to develop and see a lot more of it.
See how that works? A well thought out and reasoned answer to your question! You guys should try it sometime!