If the Atari and the ESP are running on separate power supplies want to avoid back feeding the unpowered device.  I'm not sure what a reasonable power draw from the Atari is and the ESP could consume several hundred mA.  The i2c level shifter output enable will be controlled by ESP logic.  A voltage supervisor was added to the Atari 5V supply to disable the ESP 3.3V regulator until Atari is powered.  So if just ESP is powered, it won't start until Atari is powered.  If just Atari is powered, i2c chip will be tri-state.

Rev 3 of schematic posted to Github.