+1
At least ability to overdub the sequence would be VERY useful
Poly unison - yes, not sure how useful it would be but would love to check it : )
Voice panning - exotic but cool!
Filter quantize - I can live with it after few years, but yes... same with OSCs.
Curves on ENVs - not sure if it's technically possible...
Good point on smooth adjustment of osc pitch, though I'm not usually using that in a performative way and actually find the chromatic stepping pretty useful in that case.
Being able to play three note chords with all those stacked detuned oscillators would be super useful, at least for my purposes. Would lead to some cool sounds that aren't otherwise possible on the P6. Certainly even better on synths with higher voice counts, of course, but if it's easy enough to implement, I'd love it.
Yeah if the envelopes aren't software controlled the slopes idea probably isn't feasible in a firmware update, but I wasn't sure so I thought I'd mention it.
I just think there are so many ways the P6 could be explored and expanded upon, like we haven't unleashed the full power of the hardware yet.