1) Dual (stereo) paths like Helix and Fractal, for powerful dual amp and ambient effects.
2) Improved profiling (the hw should be capable of doing this based on what CK has said several times). Kemper is amazing but is marginally bettered in terms of accuracy now by Quad Cortex.
3) Synth emulation w/ midi (this would be absolutely stellar, and put the Kemper in a field almost entirely on it's own imo)
4) Functionality and usability improvements for writing/creating, possibly via the software UI, so that looping and DAW integration is more seamless.
5) Better "one-click" scene type editing and switching (again a la Helix and Fractal). Instead of saving custom versions of profiles and adding them to performances, introduce the concept of profile "scenes" (or whatever you want to call them), and allow them to be switched seamlessly whilst remaining within the same profile in a performance.