> > 	1. A user mode configuration library that uses a protected
> > 		binary file. (a *gasp* registry)

The ultimate authority must be a plain ascii file.
If a binary file is desired for performance reasons,
it could be "compiled" from the text file, like sendmail
used to do.

> For example, imagine an RCS filesystem
> built with a user space filesystem and the RCS commands.  When a file is
> opened, the daemon does an 'co -l' on the file.  When the file is closed,
> the daemon does a 'ci -u'.

No thank you.  I often open files without wanting to do a "co -l"
on them.  Ditto for closing them.

-Dave