What's wrong with the monitor eq?
The four controls have nice frequencies for general tuning of the sound. But I would love to have also at least one full parametric band that could help me
1) cure sharp spike frequencies that some shitty backline amps have. These are narrow band resonance peaks in the upper mids. I can't explain where they come from but I had it often on old, badly cared for amps in clubs. It sounds like a nasty metalic tone but it actually is just one howling frequency. Rusty silberface Twins really like do do this and a little bit of narrow band attenuation can do magic to the sound.
2) iron out some booming low frequency resonances in the room that appeare some times on narrow, crowdes clubs when the amp can only be placed in an awkward position.
3) maybe it also helps to find a better way to connect to an instrument input with the cabinet switched off. In my Litte-Big-Amp setup with a real Champ > DI-box > Twin I used an Empress ParaEq between a fullrange DI-Box (no cabsim) and the Twin to attenuate the 3000Hz at a narrow band. That often did the job quite well.
But I still don't really understand how the KPA is able to take out the cabinet from a profile that is recorded with a mic and speaker. Seems like a kind of reverse engineering. Need more time to try out different setups with different monitor amps ...