Well, I wasn't taking the OP's idea to mean only splitting off the crawler. Why not an API where you send it the search query and then it returns the results? It could have a variety of return options including using a ranking of the API publisher's choosing or you could ask for something raw, and innovate with an even better or more suitable ranking based on your specific needs.
In the end, the point would be to make Google closer to what it was at the beginning -- just input and output. No ads on top of it, no bundling with other offerings etc. And if the publisher's ranking remains as good as it should, then surely some will be willing to pay not only for the raw data, but the ranking as well.