The idea is to be able to ring out a room/monitor for the worst case scenario using an NEQ/GEQ then dial back the cuts to a more reasonable level using one fader/knob. This would look similar to how an MCA adjusts the send levels of several channels to an aux/matrix.
Use case: One performer has great mic technique, and less EQ cuts are needed to prevent feedback, so you dial back the lead vocal bus NEQ/GEQ. Then an unexpected performer with bad mic technique does an impromptu bit in front of the mains. The engineer could use this one knob to dial in the GEQ/NEQ cuts that were configured for this worst case scenario, and revert the changes easily after the impromptu performance is done, restoring better tonal quality to the lead vocal bus.
.
