Villas:Surely, if the imbalance (for whatever reason) is not too large, AND the subsequent flight is forced to fly for a long time - then would not it be prudent to be more proactive and reduce the imbalance with differential thrust. Once the wings are balanced then the flight can be continued with the cross feed closed and each engine operating normally. ie. one on gravity and the other using the pumps. That way you don't lose significant range. And yes, I am aware that you will not find this in the FCOM.
This thread has shown signs of the old arguments that you used to get in the sim. about when to fuel balance. One school saying never do it until told to by an ECAM!
However the original scenario is so unlikely that it is almost not worth considering! I also appreciate that instructors can not be seen to advocate procedures that are not "in the book" however this is a discussion board and we may have lost sight of the original query. I personally have experienced multiple spurious ECAMs and loss of FADEC thrust control. Neither situation was covered in the FCOMs.