it would be great to have some way of doing this without requiring workarounds. This is the main reason why i don't currently use kemper for acoustic and have a completely separate setup for the acoustic. On my Helix I can do both very easily, but Kemper is a lot more limited in this regard. Having OUTPUT section as global has some significant advantages.. but, perhaps having some sort of "output override" options in the RIG section that is saved per Performance (and if enabled, defuncts the corresponding OUTPUT options) might be a good way to get both worlds.
one workaround i think someone mentioned that i read was sticking a stereo FX SEND (without the return) into the second to last stomp slot and using the corresponding FX outputs to your DI's.. then putting something into the very last stomp slot that kills the signal.