I came to think of your approach outlined when reading another thread. I think that you have a good idea. I also think people might be missing what you’re saying; not necessarily being able to put together all the parts on their own.
As for me – I realize that I reach for a functional transformer of sort. A -> chain if I’m working with maps, a ->> chain if I’m working with sequences.
Have you considered creating a package for the RMDB functions (join, index, select-by-index)? With a README example or two explaining cases where RMDB is advantageous compared to nested hash maps? And perhaps with an opinionated approach to use with threading macros?