This sounds like a good idea in the first place. But this leads to many new problems, e.g. if you change the alias a couple of times and then use a version from the past you can have conflicts. It will be a nightmare with the URL and the router. I am strongly against this.

I also don't see the benefit of adding this. In case of a menu item to com_content, the article or category could have been deleted and all of a sudden you get a broken menu item. Menu items also aren't overly complex items (or shouldn't be) so that a versioning here rarely makes sense.

While I am agree with all previous comments, I still think we can implement this feature, but without "restore older version" functionality ("read only" mode).
Because one of the advantages of use versioning is to see what and when something was changed, and by whom (especialy for sites with multiple managers).
Manager/Admin then can decide wich part they want to restore, by good old copy/paste method.
btw, same can be done for modules.

This possible future feature has been discussed in yesterday's weekly CMS Maintenance meeting.
It was decided that if someone is willing to code this functionality, then it could be merged.

If someone can code this functionality, please do.