Then instead of using 2 expression pedals, use one expression pedal (Kemper Volume, set Pre Stack) and a volume pedal (eventually stereo) after the output. This is going to do exactly what you're asking for
I agree this is the only way to do it and achieve everything JohnnyBee wants. However, I might be inclined to put the analog volume pedal in front of the Kemper and use the Kemper volume at the end of the chain. Putting the analog volume at the end would mean that FOH would be controlled by the pedal but onstage Monitor Out wouldn’t. That might be the desired result in some cases but probably not most.