That would be awesome, easiest way would probably be the option to assign an external pedal to the global volume control that is controlled by the big wheel on the left + the option to activate the tuner while on 0. Maybe add the logarithmic option like the new volume block has also for the folks that are used to the classic feel of analog volume pedals.
EDIT: The more I think about it, though, the more I think volume control and tuner activation should stay separate - at least for my way of using both: Live I mute the signal completely between two songs, when I feel I have to tune / have the time for it, I activate the tuner. But often, before the next song starts, I change the preset or scene. If the tuner now occupies the whole screen during the entire break, that would be very inconvenient, because you can no longer see the presets / scenes without unmuting the signal. My wish is therefore still that the tuner can be activated instantaneously or that all switches can be assigned to any device functions (as in the Helix Command Center).
If you feel the same, please vote for the following feature requests 