+1 Here for the “Mono” button on the Master/Main channel.
Would be great if we could preserve our stereo setup and turning it into mono, just by pressing a button.
The scenarios where are going to use the mixer in mono mode are much more than for the stereo, for live performances.
Most of the venues (clubs, piano bars, restaurants, discos…) are not designed for concerts with stereo in mind. The people sitting everywhere, sometimes even behind what is meant to be the stage. Sometimes the spaces in the venue are separated by glass walls… The only applicable setup is the Mono in such situations. And these scenarios are the most common cases.
I have mentioned other important improvements that we need in the CQ mixers in this thread:
After all the CQ series are meant to serve mostly in all those scenarios where the mono setup will be used primarily.
In these modern days options like mono button on the master channel, side-chain dynamic equalization and ducked delay/reverb are an essential things. We need, also, to be able to take the most out of the Mono setup. The good sound is 50% of the whole job.
I’m still new to A&H with my newly purchased CQ that I was able to use for two events already. Amazing mixer! 
Just for one of the events I really needed a dynamic EQ with side-chain to compress the bass guitar at certain frequency range, when the kick appeared. In another situation the vocals may need some space in certain frequencies…
I really do hope the guys at A&H are checking our requests here! I’ve seen that many requested features were added to the latest firmaware update.
Best regards,
Thurisaz