If I were to use combos for the Return could have have both plugged into the Kemper and depending on which I use the kemper would know that one was plugged in? (make sense? Since I would have XLR and 1/4" plugged in but not both at the same time for the patch pannel).
You could totally do that, since it seems like the combo sockets indeed have different signal pins for XLR and TRS.
Yet for me it would not have been an option because those sockets are not available in D-norm size and only in plastic enclosures. I like mine to be metal of course.