I'm going to throw this idea out there just to get people thinking. There's nothing in reality that is like this except maybe some of the ReiserFS ideas, but I want to take the idea farther. the idea is ......Maybe it is better done by fuse? So, did you consider contributing to RelFS or something like it? Try FUSE.sf.net to find out the present fs-in-usermode projects.
Why not put an SQL filesystem directly on a block devices where files are really blobs within the filesystem and file names and file attributes are all indexed data withing the SQL database. The operating system will have SQL built in.