I think this is a great idea. In fact, I would very much like Google to provide access to all yearly indexes. This combined with the provided web.archive.org links makes it possible to get vanished info (OK, not all web pages were archived by it, but surprisingly many were).
The web "cloud" contains information, some of which can disappear at any moment. As a consequence, many users feel the urge to grap copies of web pages (hence the use of apps like Evernote, surfulator, etc even my own SQLNotes aka InfoQube). If there was some solid searchable web archive, there would be no such need.
Just my 2 cents