Ah-ha! Found someone else who had the same thought as I did so I guess I don't need to start a new thread, I'll just bump this one.
Could add a simple hotkey function for sound channels in the mixer to turn the volume on and off, could make more complex productions with various sound inputs easier.
I'd love to see an option to add sound from individual programs as an option, but for gameplay with mumble, ventrilo, teamspeak etc. having a push-to-talk shared hotkey would be extremely nice, so that viewers can hear what the broadcaster is saying to their allies without the caster being forced to 1. tab in and out of the game to fiddle with the audio mixer every time they want to talk, or 2. be constantly broadcasting unintentional white noise that they don't want.