Mockie, this is an ARRANGER forum. SZ have a workstation forum where you might get better info...
But, essentially, I would say that if the Fantoms and Motifs HAVE multiple outs (which I believe they do) I see no reason why you can't do this.
Heck, I can even do this with my G70... (so does this make it a 'home' feature?
)
Nice to see someone that likes to PLAY the bass part around here though...