I wrote an emacs package called SFS(search file system) to solve exactly this set of problems. It is just an interface on top of the excellent Recoll full-text indexer. Among other things, SFS allows you to create hierarchies of queries, the search analog of a folder hierarchy. A parent "directory" is just the logical OR of all of it's content named queries. Everything works great for me, but the installation process is a bit painful(especially cross-platform), and indexing can take a serious amount of time and space initially, so I would say it's still a ways from being really comfy to use. But it is totally possible to have your own little google for your file system. I have gifs on the GitHub page to at least give you an idea:
https://github.com/Overdr0ne/sfs
Enjoy