First of all, FAT is patent encumbered and Microsoft's willing to go to court to protect it; so that's out. That includes the old UMSDOS file system Linux had at one time.
Someone needs to make a good file system that matches FAT, but is more extensible. A good choice is ext2 now... if we dropped a few things that wouldn't work nicely. Like device nodes, pipes, and Unix sockets. Like ownership, since it's assumed that the person mounting the system would own the files on it, along with groups. Simply access restrictions; they wouldn't apply.
This will simplify the structure a bit, which is a nice bonus and could let it be put on floppies. In other words, it's a light, anonymous, extended file system. LAEFS.
I got an .h file. Anyone want to help develop it as a FUSE driver?