As the title suggests:
De-Esser being available in dual-mono mode on a single FX slot.
There’s room on the screen to have 2 GUI’s, it supports stereo mode already, so all it would need would be two mono blocks side by side and on it’s “back panel” the option to insert too two different channels.
I understand the limitations of FX slots, but it seems everything is in place for this to be the only RackFX that could be implemented somewhat easily.
Considering a de-esser is basically just a variable single band compressor, there should be plenty of DSP power to support 2 of these in a slot.