The Key/Seq modulation source is linear: low notes produce a low control voltage, the highest key produces the highest control value. This limits the applicability of Key/Seq. It would be very nice if the relationship between note position and control value could be altered, e.g. by using a sigmoid instead of a linear function. Alternatively the range of the linear function could optionally be restricted, e.g. reaching the maximum value at n notes above middle C and reaching the minimum value at n notes below middle C.
An example for a situation where this would be useful: percussion/drums. One could control the noise level with Key/Seq and turn it off completely for low notes and enable it fully for higher notes, thus letting the key position switch between kick drum and snare sound.
Together with the proposed fast slew-rate modulation tracks in the sequencer this would allow for intricate and complex percussion programming.