Could it be possible to program a "dynamic Output EQ" in the Output-section, which could compensate for the Fletcher-Munson-Effect ?
It should have a pre-adjustable "frequency-curve" (f.e. a 15 band graphic-eq) which is ducked at low Output-Level but gets more and more in when the Output-/Master- Volume-Level-Pot is cranked.
This could be used to prepare sounds at home or during rehearsals (at low level) and make them function for live-Level-use just only by adjusting the Masterlevel-control to the stage-loudness.
At the Moment we all use the 3-band Output-EQ which has to be adjusted "by Hand" to the specific stage-conditions. But it's only a raw adjustment. A "dynamic eq-curve in Output could be a huge improvement for the live-gigging-Amateur who often doesn't get much time for soundcheck on stage.
I know, that we got a pretty numerous bunch of EQ-Parameters in many sections of the KPA, but they have fixed eq-correction and don't react dynamically. So they have to be tweaked for each rig /or Performance Slot. If you use Performances as recommended (one Performance per song) there will be no other chance to make overall EQ-Settings in the Output section.
Alternative:
Fixed 10- or 15-band Output-EQ to make finer adjustments than with Bass, Middle, Treble at the Moment.