Though not exactly the same thing, Tcl can use its VFS extension to provide a "file system" for an application backed by a database or ZIP archive. The VFS all

Though not exactly the same thing, Tcl can use its VFS extension to provide a "file system" for an application backed by a database or ZIP archive. The VFS allows bundling up an app as a self-contained executable (a "starpak") or runnable with the Tcl/Tk interpreter (aka "tclkit"). FS access is transparent to the app--read/write operations are the same for all FS types. Some work has been done to use sqlite as a VFS data storage medium. I haven't yet tried it myself, but in principle, it's not too hard to accomplish. I'm putting that project on my list...