I also dream of this feature
Cutoff-keytracking with consideration of portamento and pitchbend is very pleasant to hear when playing mono leads/bassline with high resonance
(a lot of other analog synths have this functionnality)
Maybe in a future update ? 
About the same subject:
http://www.elektronauts.com/t/filter-1-as-oscillator-not-really/9660/88323