Question

Since Ableton Live can only handle stereo inputs, the talkback (input 27) is effectively unusable.  If a dummy/duplicate of the talkback channel could be somehow added to create a 28th input, that would allow it to be used.

Answer 1

This was delivered with Universal Control 2.6

Answer 2

A stop-gap solution for this (on OSX at least) is to create an aggregate device between the Quantum and (in my case) the Macbook Pro internal sound card.  This creates an audio device with the slate mic on channel 27 and one side of the stereo Macbook input on 28.

I'm using this as the input device in Live, and keeping the standard Quantum device as the output and it seems to work fine without introducing any extra latency.  I've always avoided aggregate interfaces in the past thinking that added a lot of overhead, but apparently not!