I've just been talking to Jeremy at cycling'74 about this.
We'd like to add three special parameters: Freq, Gain and Gate. If used in the patch, then you will get the current MIDI note and pitchbend as Freq, velocity as Gain, and Gate = 1 if a key is pressed.
Of course this only works for one note at a time, but for polyphony we can create several instances of the gen~ patch to assign notes to. So it makes it really easy to write synth patches in gen (and we'll do the same thing in FAUST). And we can make it work with MPE too!
For additional parameters you can already set A to H through midi.