For each extension, an email address parameter, allowing one to click it in the panel, would be useful. I envision possibly a button parameter like:
emailaddress=
and then an icon on the button that creates a simple mailto: url for ones default mail client to take over from that point.
This is useful to a receptionist when someone calls in and after learning someone is out of the office, they decide they just want to give the receptionist a message instead of leaving voicemail. This is an included feature in isymphony And doesnt appear to be too overly complicated. Your freepbx import script that parses voicemail.conf seems as though it could easily grab this data automatically as well.