Vilas, I understand your point of view, but I believe this time you are not right. The airbus procedure maybe is adequate for lower levels but definitely not for very high levels. Like I said before, this comes from experience.
This situation cannot be "tested" in a simulator and I can assure you I already tried it in very different sim standards.
What puzzles me why worry using SB if the aircraft is in Normal Law (with all its marvelous protections). If the aircraft suddenly exceeds MMo, for sure this should be something related with a sudden change in OAT and/or wind. If the ATHR is engaged, it should do its job and the airspeed reduction should occur accordingly. If the ATHR it is not engaged, simply reduce thrust to T safe (50/60%).
Can you imagine (try to make an effort) if something happens (like what happen to the AF447) and while the SB are extended the plane suddenly downgrades to Alt Law?
Once again, good luck.
p.s. A320F = A320 family aircraft