As a side note, the traditional keyboard size is not representative of the average pianist's hand size. David Steinbuhler [3] has been making modified traditional keyboard layouts by varying the width of the keys slightly, and people rave about it. I've had the chance to visit his shop in Titusville, Pennsylvania, where he designs them. It's a totally enhanced playing experience, even for someone like me who can play a 10th without difficulty.
[0] https://en.wikipedia.org/wiki/Harpejji [1] https://dodekamusic.com/ [2] https://www.lumatone.io/ [3] http://dsstandardfoundation.org/the-standards/