There are a number of external switching devices on the market that utilize the TRS switch, most of them with two switches, but some with 3, and even 6 (TC Helicon switch 6 is one I have). They operate differently, but basically each switch has a resistor of a different value, meaning they really are expression pedals, just with buttons that swap to a specific resistance.
With the current options in the QC I can assign a single switch (or half the switches, rather) to a latch emulation that gives me one additional footswitch on the board. But It’d be cool if the unit could be trained to see different expression pedal settings as separate buttons, not just a continuous sweep.
Probably too niche to get many votes, but I know the device would be capable of this pretty easily.
Boss FS6, Strymon Multiswitch Plus, many pedals designed for amp channel switching, would all possibly be supported. Much cheaper and smaller than a $400 midi controller that many people wouldn’t need.