Doing audio repair and maintenance work it is very useful to have a 'levelled' speaker feed (ie agc applied so that there is always a residual noise) that allows one to hear what is going on is very useful. With old-skool N&Ds one could listen post-notch (no so easy with FFTs...) and easily hear what the distortion type and hence what the problem is.
Some modern instruments (eg NTI XL2) still implement this speaker/monitor and post-notch capability despite being fully digital.
This would be a lovely addition to Multi-Instrument!