One strange direction to explore could be to set up a webserver to serve a directory full of files, rig your db to look like a filesystem, then compose the two.

One strange direction to explore could be to set up a webserver to serve a directory full of files, rig your db to look like a filesystem, then compose the two. This is a probably a daft idea but searching "fuse postgresql" produces results, so it should be an easy daft idea!