Cool idea. IMHO traditional information retrieval is the way to go with RAG. Vector search is nice but also slow and expensive and people seem to use it as magic pixie dust. It works nice for unstructured data but not necessarily that well for structured data.

And unless tuned very well, vector search is not actually a whole lot better than a good old well tuned query. Putting everything together, the practice of turning structured data into unstructured data just so you can do vector search or prompt engineering on it, which I've seen teams do, feels a bit backwards. It kind of works but there are probably smarter ways to get the same results. Graph RAG is essentially about making use of structure of data. Whether that's through SQL joins or by querying some graph database doesn't really matter much.

There is probably some value into teaching LLMs how to query as well; or letting them interface with existing search/query APIs. And you can compensate for poor ranking with larger context sizes and simply fetch a few hundred or even more results with multiple queries. It's going to be a lot faster and cheaper than vector search to scale that.