I was just looking for the same thing. But, thinking about it, you'd end up having more than one account share the same home directory. If you were chrooting, at least. Which you would be, unless you wanted to give every user access to everything on the server.
hmm... I think you'd end up with something like:
/var/www/vhosts/example.org
-- httpdocs
-- users
---- username
------ chroot dirs
------ link to httpdocs
---- username2
------ chroot dirs
------ link to httpdocs
but I think I'm missing something... In any case, I think it could be kind of complicate, but I'd still like to have it.