I suggest a diff format, that would be then merged into your project repository.
This will turn Inspector into a WYSIWYG development tool. Awesome!
A heads up for someone when they start working on this. There is already quite a bit of existing support for CSS Style changes and a hidden Changes View (a separate view that shows up inside the Drawer that contains the Console View). There are comments in the code that point out how to enable the Changes View. And you can follow comments and function calls to find what functionality already exists. Its something I started working on but couldn't finish due to school work.
Also see my comments to saving in bug 20663. Again, I think as soon as somebody starts working on this, a more generic ticket is needed.
Paul, you may be interested in this bug:
We are tracking an ability to export CSS in 38578 - Marking this as a duplicate
*** This bug has been marked as a duplicate of bug 38578 ***