I am not so sure about that... a lot of arranger users are befuddled by the comparatively simple OS's and voice and effects editing they already have

Shoehorn that with the complexity of something like the MoXS, and I'm not sure you wouldn't end up alienating most of the target market...

The S90/70XS new 'live' keyboards from Yamaha seem a step in the right direction, marrying most of the MoXS's power with a simplified OS, and expedited live control functions. If these are successful, perhaps some of this live ease will trickle UP to the full WS OS?
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An arranger is just a tool. What matters is what you build with it..!