aliases under the complete control of users?

[http://dummy.us.eu.org/robert (robert)]

I would like users themselves to manage their aliases.  Right now, I'm doing
this:  I create a file in /var/qmail/alias:

.qmail-alias1

with this in it:

&user1-alias1

Then, the user has in his home directory:

.qmail-alias1

with this in it:

./Mailbox

(or whatever).  The problem is that adding new aliases is a pain because
I have to do it (I'm the one who installed qmail).

I saw in the qmail mailing list archives discussion about making
/var/qmail/alias writeable (in some fashion) so users can add their own
aliases, but I couldn't see a resolution in the discussion whether this is
feasible or whether some users could end up eliminating other aliases
unintentionally.

Perhaps there is a software package to do this?

Thanks.