1. The origin of Nurion story.
2. The metaphysics/planes
3. The alignments
I don't think it will be too hard. The origin story and alignments will be fairly easy, once we have the new planar system hammered out. I have been a bit disatisfied with the Farland planar system for 3.5; the names and description of the planes are unoriginal. This will be a good opportunity to redo them.
Let's start with a list. What are the planes in standard 4E (my DMG is at home and I'm at work)?