I still think and hope that the film will show how Clark learned how to fly for the first time and doesn't leave that lesson off-screen.
I want to see a period where Clark didn't know how to fly, portrayed by Cavill along with seeing on how he eventually learned to grasp that power and his reaction to it. I think it would show good grounds for development.
Also, a part of me thinks that Clark won't necessarily put on the suit until Zod makes his appearance causing havoc in the world, which probably leads to one big disaster that calls for Clark's attention.
HOWEVER, I do think that Clark will be proactive in saving people, albeit in the shadows or as himself but somewhat concealed, before then. So that way, he won't be shown as the "reluctant" hero. Perhaps before Zod's attack, Clark will be shown wondering on what he should do that would be in the best interest for everyone which leads him to realizing that the world needs hope, hence the donning of the suit.