An interesting topic! I have seen sites with functionality along these lines:
- Travel sites that inform you whether you can get better prices if your dates are flexible.
- Ecommerce sites that present similar products that optimize for a variety of objective functions, e.g., top rated, most popular.
The general principle is to see whether there are plausible alternatives, and if so to expose sensible trade-offs to a searcher.
That may feel less ambitious than have a fully-fledged conversation with the searcher. But I think it captures the same spirit: recognize the complexity of the search task and help the searcher understand and execute the decisions he or she needs to make.