That's a great question Sam and one I have a particularly keen interest in knowing myself. If you happen to have posted this q elsewhere and get an answer, please share it with us. I'm very interested in the possibilities of a potential arranger / algo hybrid.

To that point, I've used some elements of the PA80 styles, along with pieces of other midifiles, including my own real time playing, to make arpeggios on the Motif with varying degrees of success. I don't know why some come out better than others, but even the techs at Yamaha that post at Motifator don't seem to totally have the inner workings of the arp mastered. Others have used styles to create patterns or phrases in the pattern sequencer.

The Motif's arpegiattor is sophisticated for an arpeggiator, and the phrases are also useful, but neither are the same as the GEs of Karma, which function more like an arp with algo functions.