On the IAE we have to call "power set" between 60 and 80 knots.
The lower value is to allow the EPR to 'grow' to the T/O value which will only happen beyond 60 knots.
Your discussions about N1 are interesting. On the IAE when the FADEC calls for an EPR, that is what you get regardless of the N1s. I suppose that we would never see a low EPR because the fuel will just be pumped in until the EPR reaches the rating. If we were over the limit for N1. N2 or EGT then we would see an ECAM.
If there were an EPR probe fault then it might be possible to get a mismatch on the N1s etc, This would then be a clue that there was incorrect thrust being produced, along with the assymetric effects and the smaller speed trend vector.