[Exim] Managing .forward outside of $home

So I want to move users' .forward files into some location on the mail
server to avoid problems when the home directories are unavailable and
to eliminate some permission problems (users doing chmod 700 ~, etc.)
Of course it is trivial to configure Exim to accommodate any
arrangement, but I'm concerned about how to manage user access to the
data.

Do other sites do this kind of thing? How do you allow users to
change their .forward files? I can see everything from requiring that
they login to the mail server and run an editor to a web form that
does it all for them, but I'm curious as to what's available before I
go trying to cook something up.

Thanks,

- J<