I quickly mocked this example yesterday so people could get an idea of how that would look. I really don't like it, the button would be way more distracting in the middle than in the corner.
As for reverting the whole thing back to how it was, the images being slightly off-center because of the 34px collapse bar has - for whatever reason - been one of the main complaints about the reader since the time it was created. We've even had people claiming it's one of the reasons why they're still using legacy.