Do you otherwise have no spare pins? Also you can do communication between halves with only a single pin, what protocol are you using?
The other thought is, does the LCD use i2c and are you using i2c between halves too? If so, does the LCD modules have a way to change their i2c address so they don’t conflict? If so you should theoretically be able to have all of it share the same bus (the same 2 pins).
Do you otherwise have no spare pins? Also you can do communication between halves with only a single pin, what protocol are you using?
The other thought is, does the LCD use i2c and are you using i2c between halves too? If so, does the LCD modules have a way to change their i2c address so they don’t conflict? If so you should theoretically be able to have all of it share the same bus (the same 2 pins).
Oh that’s an interesting thought. All might not be lost after all! I’ll need to investigate.