Nearly every president makes promises prior to gaining office that they have to alter or change completely once they have full information. Take Obamas stance on Guantanimo, for instance, or even his first plan to stimulate the economy. He ultimately went with keeping gauntanimo and allowing Bush's original stimulus plan to take effect during his presidency.
I honestly think Mitt understands that he doesn't have all the answers. He has a vision that encompasses his platform, but he understands that if he comes up with a bunch of ideas now, most of them are going to change once he's in office and has access to a lot more information than he has access to now.
It's been a long time since I've been able to trust a president that "has all the answers" during their campaign. Too many times they'd changed things significantly.
It's like the guy who said, "I used to have seven rules about raising kids. Now I have seven kids and no rules."
Besides, he's running his campaign like he's running a job interview for position of CEO. He doesn't come into the job micromanaging - he comes into saying, "I want America to look like this at the end of my presidency. Now how do we get there?" and he lets his advisers advise him.