The WordPress 4.6 roadmap for the Customizer is being formed, and here’s a sneak peak. Features being considered are basic content authorship in the Customizer and Customizer Transactions, which would allow revisions to changes in the Customizer, among other perks.
I’d love to see a “new page” ability in the menu customizer, because that’s a common new site activity that requires a lot of URL juggling right now.
