randomization and more scales would be great.
my biggest personal desire is for programmable/user-defined scales and arpeggios, or a programmable algorhythm that would let you achieve counterpoint with the harmonies. i.e., you set your scale, key, and the harmonizer would play intelligent harmonies that were not just a fixed voice above/below the note you play– they could be, say first 2 notes, a specified interval above, and 3rd note a specified interval below. there could be a number of different "counterpoint" algorhythms defined, just as there are multiple arpeggio patterns.
it seems that the harmonizer has all the tools there to do this, it just needs to have the option added. this would make the guitar parts sound more natural and "human" the next time you want to play harmonized iron maiden riffs or whatever– counterpoint would also sound better for the more orchestral voicings like quadravox. you could play one-finger string-section parts, little chamber music pieces, whatever.
that, and the ability to user-program arpeggio patterns and scales, would make the pitchfactor truly dreamy. i'm still learning to use mine, and there are infinite possibilities, especially with the aux switches/second foot control. i've waited years for a pedal to come out in this format and price range that does these things– this kills the whammy and everything else on the market.