Well in church we layer sounds on the fly. And adjust layers as we move through the service. Or.... Bringing various elements in and out during a song. (So that could be used in alot of places outside of church)
Like for example, a
piano and string or pad. Or a piano with a synth layered on top. Then you just adjust the faders for whichever sound you need more or less of. Make sense?
As I mentioned, Keyboards like the mox, MOXF, Nautilus, etc.... Don't have faders so they don't allow "fader" control of sounds in your set.
In your example with the Nord, you would route all the sounds out of the different outs. But if you only have 2 sets (or stereo, so four outs), you won't be able to be as flexible as the keyboard that has 6 sets (or 3 stereo pairs of outs).
With a setup like you mentioned, it may be beneficial to uses busses out of the mixer.... So after everything get to the mixer, you then bus it out accordingly... So like synths on a bus, organ on a bus, etc ... And only saying that since your setup is so complex and sounds are coming from so many different sources.