uneducated hint for improvement:
add zener between USB5V - teensy 5V - lynx 5V. that way teensy is always supplied with 5V, but neither will LYNX drive the USB of your PC, nor the PC usb power your lynx (for safety). But make sure GND is common for all and connected
use 244 instead of 245 for data pins, this saves you the direction.
for address pins, you can use even simpler chips, as you do not need the "enable" at all, simple i2c level shifters may do
if you add comlynx, you may want to use also simple chips (e.g. I2C level shifters). dont forget the diode between RX and TX, otherwise you cannot send from Lynx side. suggest not to connect comlynx 5V to the rest beside the comlynx level shifter.