FWIW, nobody misses 2 amps at once because the 1:1 realism you get out of a Kemper profile never lets you miss anything to 'enrich' what's already there.
When I had the Vetta I almost always wanted to use this feature.
Personally the best amp set up I had used a mix of an OR15 for mids and highs and a 5150 II for the grunt and low end......the OR15 was my main sound and the 5150 was blended in via a volume pedal.......but it was noisy regardless of my use of ground lifts and ABY switchers with isolated outputs and phase inversion etc.
So, if I could have a profile that allowed me to have a fixed mix, or even better, a way to blend those 2 amps via an expression pedal, I'd be in heaven