That doesn't solve the discoverability problem for good, as the 404ing links will themselves be removed after a while; what we really need is a good search engine for the archives.

Of course, the whole point of this article is that centralisation of important resources is risky. Archive.org is an essential resource, and it's really far too important to be at the sole mercy of the of the Internet Archive organisation, well meaning and admirable in every way though they are.