- many user programs will need to be modified to include the
   	  correct headers

why?

   	- kernel sources will have to be moved
   
   I personally like something like fs/ufs, fs/nfs, fs/ntfs... I don't
   think that classify them further serves any useful purpose except
   adding bytes to source files.

i agree, including what cgd said about ufs_common..
   
   While we are at it, why don't we do the same for net?
   	net/{inet,ccitt,atalk,iso,natm,ns}
   
   Then we can break *all* userland programs that use the network.

i don't see why moving the kernel sources around has to do with
breaking what the userland sees?  that's why we install headers
individually from each directory now, isn't it?

   But that is easily repairable by ln -s net/inet netinet in /usr/include

this just seems gratuitious.  if we need /usr/include/netinet,
just use it and don't litter /usr/include with symlinks that
serve no purpose.
   
   And finally, we can go the solaris direction and move all the fs related
   commands into separate directories and leave only the central command
   behind.

i do like this idea...