Hi, it’s more than possible that there is a limited amount of code space left in the Super 6 for a luxury reverb algorithm. But does it really a complex algorithm? Maybe something like the MIDIVerb 1 but with a little modulation so it’s not so static and ringy? I’ll leave this web based MIDIVerb emulation to show what a compact algorithm sounds like. 
My other idea, to select reverb, maybe turn the delay level down to zero, then it becomes reverb when you raise the level again, turn it down again, it flips back to delay, and so on… Or maybe just hit Shift and turn the level knob to flip back and forth so it’s more intentional.
The knobs: Level and Time, would impact reverb the same as delay, Feedback might be best used for Colour, maybe a medium-wide bandpass that goes from a dark bassy reverb to a “normal” midrange reverb to a bright shimmer, might be more versatile that a low pass.
http://ibawizard.net/midiverb/
Thanks!