Thank you for all that great Info Diki.

Its obvious that most arrangers are still build to function as a standalone instrument.

Only Korg's PA2X was build with master keyboard functionallity in mind. And even the PA2X is far from ideal in being on the receiving end.

Is it so hard to see that a Wersi Abacus dua pro configuration with or without pedals is something a lot of Yamaha fans would love to see, with assignable instruments to 3 zones on the uppper and 3 zones on the lower keyboard...

Its all about flexibillity... in performance A i want to play the Upper keys as an arranger while having a full lower keyboard available for a piano part...
Or in performabce B having 2 solo insruments on the upper keys and 2 solo instruments on the lower keys.

15 years ago i had a WX2 from GEM that allowed full flexibillity in setting up the keys i could layer 8 sounds over the keyboard every sound having its own range. and then add a splitpoint for the left hand chord recognition on top of that.