Basically, I'm completely with you Burkhard. With more than a thousand gigs in the last 6 years (where my KPA has always worked smoothly), I have certainly substituted in 50 to 70 different bands. Everything was there from the pub gig to the stadium thing. During this time I was mostly dealing with very professional people, digital console and app for mixing the inear signal included. I would call that the standard today. Unfortunately, I also had to deal with sound technicians with hair-raising knowledge and miserable equipment, or with small acts with bands that completed the gig without sound engineers and only have minimalist sound systems.
Since I always work with Inear monitoring, I usually send the inear signal to the Kemper to be able to add it to my own guitar signal in the volume as needed and use the KPA as a monitor mix console. This works perfectly in 90% of all cases. If the Inear signal from the console already contains the guitar (for example a main mix or a mix signal, which I have to share with other musicians, as there are not enough aux channels), a mute function of the guitar signal in the headphone-out would be extremely handy to avoid a duplication of the guitar signal. This feature would be very helpful for all these exceptional situations. In these cases I could save an external Inear system and use the KPA for inear monitoring as usual.