A plugin bundle utilizing the PEAR LiveUser+ authentication framework
is separately available in the /plugins/auth-liveuser package, with
its own README file. It is even much more sophisticated than our
_perm_unix plugin, and provides user friendly administration pages.
prev << "users_ldap"
next >> "Terminology"

You cannot modify the ProtectedMode file, but anyhow any ideas or suggestion should as usually get filed on BugReports, UserSuggestions or even better the ProtectedMode.Discussion.