The trouble with built-ins, Donny, is that you HAVE to pay for them, whether you want to use them or not!
I've no use for mine, and would have happily paid $800 less for the G70 without one..!
I'm STILL trying to convince my audience that most of what they are hearing is actually being PLAYED, rather than karaoke. Add in a bunch of harmony parts that they can see are obviously not there, and that becomes harder and harder to do. Might as well just use mp3's, and record REAL harmony parts (and guitar parts, basses, whatever) and go full karaoke... (and save the money on the box).
Plus, I'm an old Beach Boys and Beatles fan (especially Beatles for harmonies), and counterpoint is what I prefer in good BV's. Something not so easy to do with these boxes. So, I would prefer that the cost of them is not included in the basic arranger cost, and those that DO want them have the choice of which they use. As you are finding out on the S900, whatever cost that built-in adds, it's money down the drain. You HAVE to buy a better one, anyway!