Uploaded video demo:  https://cdn.hackaday.io/files/1797867691964224/Rev%202.1%20Demo%20Small.mp4

Going to use a dedicated level shifting chip TI TXS0104E for the i2c level shifting.  This has 4 signals so will let the IO expander handle SCL SDA, the IO expander interrupt feedback, and feedback if the Atari is powered.  While picking this chip noticed the 1M digital pots weren't in stock any longer at Digikey in TSSOP package...