I'm working on a new AGI-based voicemail system right now, which is pretty close (a day or so away .. if the rest of the people in the office will leave me alone and let me code, anyways.. ;) ) to having full functionality of the current app_voicemail in 1.0.5 (and will remain almost fully compatible*). One of the things I'm working on as a part of this is a web-based interface to voicemail, including a way to change mailbox options.
I could certinally add a group distribution list, both defined in voicemail.conf (or whatever backend**) and on a per-mailbox basis, that could be configured either from voicemail, or from the web interface (which would probably be more user-friendly).
- compatibility issues are only with where to store options. I'm not rewriting voicemail.conf at all (like app_voicemail.conf does) on password changes etc, and instead using the asterisk db. This could be easily changed using a different backend** however.
- there is a pluggable backend system that takes care of all permenant storage issues, including loading the mailbox info, changing passwords, getting/setting options. This could be very easily modified to not use voicemail.conf at all, and use a mysql/LDAP/whatever backend, or to only use voicemail.conf and not the asterisk db. I was concerned about concurrency issues, however - there would be locking issues if you get too many people in the voicemail system at once.