Google and the Internet Archive already caches it. Also, if your work goes down for whatever (perhaps legal) reason, you know that people can still benefit from it.
Caching it for when a site is overloaded is not ripping it off, just like sending copies of works to the British Library for archival purposes is not ripping the original work off.
The trick in this solution is deciding when to flip the switch for the cached version.
Perhaps a simple GET to the URL ever 60s. If you receive 5 non-200 responses in a row, then the HN link points to the archive.is version. Same method in reverse for bringing it back.
That sounds like it would DDoS the site.
Even better: monitor the comments for "site is down", or just provide a link to google's cached version as a button (Even better than the 'web' link we have at the moment).
Both of those sites can be instructed not to store copies of your pages for their caches or archives; and they will dutifully follow your instructions.
Also, the library analogy doesn't work in copyright law. Copyright protects the act of copying, not the act of transferring an already-authorized copy of a work to someone else.
