[RFC] "final" flag for a directory

Hello,

I had an idea about adding a boolean flag "final" on directories in an
advanced filesystem.
In the same way, the "final" keyword on a class in OOP can be added to
declare no subclass can exist,
the "final" boolean flag on a directory could be added to say that the
directory has no/must not have any subdirectory.
So here we see that 2 flags could be added:
- a configuration flag "must_be_final" forbidding to create a subdirectory,
- a status flag "is_final" telling that no subdirectory currently exists.
I think it may allow some small optimizations.
With a very limited search on the Internet, I found no similar thing before,
but I do assume that I'm not the first one to have this idea of
marking the pseudo-leaves of the filesystem tree.
Please, let me know if this should be discussed elsewhere.

Have a nice day, best regards,
    Laurent Lyaudet