Arrangers are a means to an end. They provide artificially what the musician cannot provide naturally - for better or worse. Give me a great drummer, bass player guitarist and horn player at my beck and call and I'll drop the arranger.

As for the video of the young girl playing, she sounds as good as a theatre organist. Is what she's doing any different. Long live the organ. I'd prefer an integrated 2-manual keyboard (and maybe some pedals) to two separate keyboards any day.