Allow audio sent into the inputs to be incorporated into the synthesis, it would be nice to be able have external audio to FM the operators, modulate the filter, trigger the LFOs and envelopes and so on, the V-Synth XT could do some of this and it was a great feature.
Individual note lengths and velocities for chords.
Feedback for other operators, more algorithms.
Use track buttons to mute operators.
Portamento with rate and time will fit nicely on those 2 blank squares on trig parameters page - just sayin! Essential