It shouldn't cost anymore really. It is really just an addition to the software which wouldn't increase the cost of the hardware. Maybe some more ROM, though in the case of a keyboard like the the Kronos it would just occupy some more hard drive space. The cost of style software development would be paid for by the extra sales to arranger users just the same as it is now even though currently they are having to buy a different product.

And I don't think any stigma of arranger features would matter if they were just another feature on a WS. Like the realtime control provided by a Karma they are just another performance tool to use if you choose to use them. I think the stigma only exists when that is the primary focus of a keyboard.