[Serusers] Register with an alias?

Hi, I'm trying to get the following functionality working (which may be impossible?) - Users have account (in subscriber table) with a numeric identity, say "1234(a)sip.acme.org" - Create an alias of this person so that they can be called by a text string, say "fred(a)sip.acme.org".org". This is in the alias table pointing to sip:1234@sip.acme.org Everything works fine. someone can call either "1234" or "Fred".... Now "fred" wants to use his text name to Register as the number is not used any more. In other words I'd like to lookup("aliases") before authenticating. (eg map from "fred" to "1234" and then verify based upon the password in the subscriber table for "1234"). Is there any way to have two (or more) 'subscriber' names get to the same auth info for Registration? Thanks for any pointers...