Even if you were able to (i.e. using Mac OS X Server), when you restart it you would have to unshare and reshare it. Something about it's broke which is why you can't do it freely in client OS X. Maybe once that's fixed....
I'm not sure if it's because the simple point of the disk identifier changing after rebooting or what, but it breaks after restarting and you end up with a folder, instead of a symbolic link, in your /Volumes folder.