That's a nice-to-have but certainly no must-have. Even if each work of art had an average of say, ten rips - unlikely, given the cost of making a rip and the loss of utility for making the 10th rip - the cost for yet another petabyte is hardly a problem (consider the analogy with software performance and additional resources).

As for the "best rip problem" ad hoc meta-solutions like NFO aggregation sites will arise where tagging would be of most use. Good old regular expression can also do some good for those who wish to have a smaller and cheaper hard drive.

You could narrow down the possible matches to just a handful by comparing movie lengths – say, within 10 seconds of the same length is a possible match. Maybe throw in some basic title comparison to narrow the search further, and then do a simple check to see if the audio tracks seem to line up (an exhaustive comparison isn't necessary) to rapidly detect and exclude duplicates with a more than adequate accuracy rate. It would require a bit more complexity in the Kopime device, but not so much as to make it impractical.