About mumble as an option:
Mumble is great for real-time conversations but is too engaging for the idea I have in mind. Mumble sessions with delegates is a good thing but isn't on the topic at all.
It requires additional software/servers and more attention from all the participants.
I don't understand your objection, perhaps because I don't know your final objectives. Why you say its not on topic.
There is already a mumble server, you don't need another one. Many of us already have the software. Nearly all the options require some software, right?
if we were to use mumble, it wouldn't be like the 'sessions' we have with BM . I think there would just be a private room that only delegates have access to. You can create your own private room and only people you invite could join the conversation.
I don't want to give the impression that I'm pushing for mumble, I'm not, just trying to understand your objection.
I think what mumble lacks is video, as well as a simple account messaging system. I can't send a message to someone if they are not connected. I can't request a 'hangout' within the system if people aren't connect. etc. so it seems it may not be ideal.