Right now I use the mixer to make ambidextrous throttle hold switches. Both top right and top left switches will activate Throttle Hold. It's great for guests. But it's a pain and I can't do it in the Standard GUI mode on my 8S or 12S.
What I propose is you keep Throttle hold and add a second "Kill" switch.
It would activate Throttle hold and set Pitch, AIL, ELE and RUD to 0.
This way you wouldn't have to have an extra pitch curve for "Kill mode" and it would be nice to have one way to kill it and still have some control, and another to kill it and center everything for quick zero pitch and swash leveling adjustments. Then you can put "Throttle hold with auto-rotation control" on one side, and "Throttle Hold - I'm gonna crash" on the other. In a panic, a guest that hits the wrong one will still get most of the benefit.