What I'm looking for here is a way to have a group chat, or a parcel, set to be a moderated forum, where the ability to chat (text and voice) can be switched on and off easily for participants.

Or in other words, where you can have one or more moderators "pass the mic" to someone so that they can talk (in voice or text). This would help in support forums, and when having meetings for example, like the roundtable meetings with the Lindens and the User Group meetings. In group chats we have a way to do this, but giving someone a group role for a few minutes only to take it away again is cumbersome. And this does not exist at all for parcels except for voice with the same cumbersome procedure to "pass the mic" and then take it away again.

For those who know IRC (Internet Relay Chat), you might know this as channel mode +m and the channel user mode +v and -v for giving and taking away the ability to chat in the channel.