An excellent idea and one (related, it was a tunable vector search engine) I had 5 years ago. One of several big projects that I have failed to get going. Sigh. At the time I wasn't a good enough hacker to generalize it for public consumption. Now that I have the chops I'm too busy to work on a(nother) big project. Though I do think it's a good idea and I think there was a CDBI auto-index module I could look at for approaches... So many fun ideas, so few tuits.