FYI - St. John Paul never commented on the Argentinians proposal, nor did he use the word “impossible” in dealing with this topic. Had he done so, he could have made an infallible proclamation, which he did not do. What he wrote was:
I wanted to clarify this because exaggeration of any kind must be avoided. Not all the Church leadership is in agreement on what can be done and cannot be done to implement Amoris Laetitia. There really should be more tolerance of disagreement here simply because there is not infallible proclamation made on this topic.
Maybe one will come out. I do not think so because of my own thoughts on the subject, but I also know I may be wrong.