I'd like to see the ability to have a true AFK channel where ALL audio messages become suppressed. Currently you can deny Speak, but people in the AFK channel can still hear when people connect, disconnect, join channel, etc. If possible, I'd like to see it where people joining the AFK channel are also automatically deafened as well based upon how you set up the permissions. So they would be able to be muted and deafened automatically when joining the AFK channel.
People currently in an AFK channel can still hear when someone joins or leaves the channel, connects or disconnects from the server, etc. Often people will go to an AFK channel to watch a video online (YouTube, etc), watch a movie on their computer, listen to music, numerous other things. Because of being able to hear the join/leave/connect/disconnect messages, they often have to Deafen/Mute self to avoid hearing these messages.
This is one of the highest requested features from the people who connect to my Mumble server.