As the title says - I would find it very handy if the Loop stomp had a SEND level control. Does not seem terribly difficult to do.
Kemper's loops, especially post amp, tend to run somewhat hot for some effects creating clipping.
This can be circumnavigated (adding a hardware pad box after Kemper, turning the amp volume down in Kemper) but neither is very practical. I particularly dislike messing with the amp volume as it throws the rig out of balance.
So, the ideal loop would have send/return/mix controls.