Yes, I have, only once though. I was once writing a story about a girl and her changing relationship with her parents. About a month into it, I realized that her sister was a much more interesting and relatable character. I had to switch alot of things around but it was definately worth it.

Nathalie, it's a critical choice, what is your narrative perspective. In fact, it's also a great way to brainstorm ideas for movies. For example, Snow White and the Huntsman tells the story from the perspective of the Huntsman. Wicked, the hit Broadway musical, tells the story of Oz from the perspective of the Wicked Witch.

It's akin to an exercise you can do with archetypes: Switch Protagonists, a great way to explore each of your primary characters and see the universe through their eyes as the main player in the story.