Look... this whole thread is about Jordan Rudess; well, he is so technically proficient that could record whole songs in a matter of minutes, meaning that he could record all the parts (including the drums track) in a single take from the beginning to the end, no matter how complex they could be.
This is to say that he has absolutely no need to record single snippets of a song like intro, variation 1, 2, 3, 4, fills or ending the way a common mortal would do (maybe in step mode).
And this is exactly what Rudess does with his Kronos: he pre-records whole tracks and then plays along them in his live concerts/shows. So, why in the world would he play an arranger keyboard?
And why would he like being associated with an instrument that has buttons with labels that read "Ballroom" or "Ethnic/Folk"? These guys have an image to look after and their followers can be unforgiving: you make a "faux-pas" and you are screwed for good.
There has been only one instance when I saw a famous artist playing an arranger: it was two years ago at a Winter Namm. Peter Baartmans was doing a demo of a Tyros 4 and all of a sudden Keith Jarrett appeared behind him and, after the dumbfounded Baartmans gave him his seat, began to play some of the scat voices, doing also a decent EW&F cover.
But Jarrett is sponsorized by Yamaha and was there to try the new Yamaha grand pianos; I bet that some Yamaha executive had the idea of asking him to sit at the Tyros for everyone to see... but I doubt that Jarrett did it for free!

Here are two videos referring to the event; BTW they were posted by Scott Yee: