You could simply make all content versioned, with a full history available. Browsers would probably want to show the "latest" content by default, but they could implement a function to view previous versions or even to highlight changes. Ideally versions would come with Git-style comments so you could read the reason for the change.
This would provide an amazing archive for anyone wanting to see, for example, what was on a "front page" on a certain date. It would also let you see if someone had altered a specific article for whatever reason.
So in theory an archive.org type entity could continue seeding old versions of websites, allowing you to go back in time, and it could be verified that it was an older version? If so, that's a good compromise.
For sure! And the URLs aren't theoretical - you can view an older version of my own blog by adding '+version' to the end of the URL. Like so: dat://kickscondor.com+1600/.
This would provide an amazing archive for anyone wanting to see, for example, what was on a "front page" on a certain date. It would also let you see if someone had altered a specific article for whatever reason.