Not just a saturator but rather a saturation EQ. Similar to WavesFactory Spectre.
The idea is to only add saturation where a positive integer has been applied to the frequency spectrum. When you add saturation to the full spectrum, you get saturation in areas that you dont want it. Most of the time, I find that the best way to enhance a high gain distortion sound is to do a 2nd stage of frequency-specific saturation (usually between 800hz and 4khz). Having the ability to control for the width and amount of saturation would be ideal. This doesnt really sound like an equalizer. It sounds more like a harmonic enhancement within a limited/controlled spectrum. I do this in the studio often when I want to add a bit of spice to a guitar sound but I dont want to add more volume to a specific frequency range.
Please take a look at WavesFactory Spectre and see if something like this is possible. Anti-phase parallel sidechain (your signal + your signal in anti-phase with an EQ modulating one of those signals) that feeds into a saturator and is then combined back with the original signal.