It would be killer to be able to profile the monitor output, amp + cab, to correct the dynamic and the frequency response of the monitor out chain, in order to make it reasonable flat. This way, profiled amps and cabs would sound very close to the originals even on the monitor path.
Imagine to profile the environment (home, room, studio, stage...) just before playing... !
When a frequency is dead on a speaker there might be no way to iron that out. Mainly frequencies that are too loud can be reduced until they are as loud as the weak frequencies. But this might end in an unsufficient volume and pressure. Speakers and cabs have their physical footprint and that's something that you can't dial away. Like when you try eq a womans voice into a mans voice, eqs alone can't do that.
I partially agree on some difficulties to make it perfect, but there are quite similar to cab profiling. There isn't extreme dead frequency on a speaker and no frequency/formant shifts as for male and female voices.
In studio, we're usually able to transform a cab to another one just with one parametric eq close to the roll-of frequency on the initial take.
