Big Idea What?
The problem with the 'Big Idea' approach is that it is always a challenge to see how it will live or die. And more often that not, you end up getting the idea approved, and then struggling to make great ads etc. on that idea coz you didn't think of that before. On the other hand, why not think real integrated? Think of one solid execution with a spine. Then find the line for it - which becomes the big idea. Then we find other executions. Alternatively, if you think of a big idea, while the inspiration is fresh, figure out the one big execution with the spine. That will leave little less to be desired. Coz if you've cracked that big execution, you are sure of how the idea lives in the world. And that's when you'll be able to present it in a way that is irrefutable. If it's truly good, that is.