Currently there is no allowance for using a full stereo fx loop (stereo out and stereo return) in the post amp slots. This functionality could be added and the user would still have full monitor stereo out in the Stage (use a pair of sends as a stereo pair and a pair of returns for the stereo return) and at the expense of Monitor Stereo in the Rack/Head models. Being able to use the Kemper's own stereo FX in combination with external units would be very useful.
One other consideration: using the FX loops without necessarily losing an FX slot. This approach was used with the Space effect - where it can be set to active in the output section and operate without consuming an FX slot - this would be a great option for FX loops also. They could be switched in and out by use of the Kemper dual Switch for example or by MIDI or just left permanently in the circuit as with a hardware guitar AMP effect loop and external effects could be bypassed or activated on the external unit directly. In this scenario, the location of the loop in the signal chain (eg between X and Y) would be a setting in the menu.