Hi @tkrieck,
I like the top icons. I will enjoy not going all the way down on long pages and I won’t miss attachments so regularly as I do now.
For my use, I prefer having a long list of versions on one line, this is easier to find scroll visually. As long as we still have the history viewer, it’s not a problem. Maybe a link to the viewer should be provided in the tab.
About the extension point, maybe it could be done the Firefox way with its extension button. This would still hide the extension, but it would be separated from the page menu.