Inspiring thread! I took on my own “A4 only” challenge this weekend with my mk1—no other gear allowed. 
I tried to squeeze every bit of room out of the four voices, using sound/parameter locking, trigger conditions, slow delay, and big reverb to create the illusion of more elements and mask the voice stealing. Spreading different motifs across patterns also helped with the live arrangement. Only post production of the recording in ableton with some eq/compression/limiting.
Have a listen/watch if you like: