@iamrobertandrews
You would need to create an acf/update_value filter for the taxonomy fields. In this filter you would need to:
1) Get the current value of the field before it will be updated
2) Compare the old value with the new value to see what relationships are being added or removed and update the other end of the relationship accordingly.
3) When updating the other end you will need to get the value of the other end, add or remove the new relationship and then update the other end.
