Can I change my outline after I've written a draft?
Yeah, it happens all the time; that's what revision is all about, right? You've decided on a sequence of evidence that you want to present, and you've got a draft, and you've realized that in fact the third point that you've made would be much more effective as your first point. So revision isn't just proofreading; it isn't just correcting minor errors. It's reconsidering the decisions you've made at the planning stage, and seeing if they were in fact the right decisions, and making the changes that are necessary if it turns out that they don't look like they were the right decisions.