I'm not too familiar with the IPS-33 (the Digitech model in your tags); other than gear-lusting after it when it debuted. I'm trying to figure out exactly how it works, and the effect that you're after. Would that be a "static" chord [based on the selected chord from a pre-programmed list], or a "dynamic" mode, where chords are detected from MIDI note input, and the intervals shift to match the MIDI input?
It's possible that you mean a HarmonyMan-type effect based on an audio source through a sidechain input, but that'd be a major hardware/software redesign for the PitchFactor.
At any rate, I've toyed around with a PF emulation of the Eventide H910/949, using that algorithm, and the parameters defined in the Clockworks Legacy manual. Section 7 / page 29 lays out the MIDI procedures.
Since this isn't an internal feature, it requires an external translation from MIDI note to CC value. I've gotten far enough for 'proof-of-concept', but I haven't made it to a refined finished state on the translation. I've also used an envelope follower (or LFO) over MIDI to trigger the Flex / Key LEARN in the Diatonic & QuadraVox modes. That, along with another MIDI message to change Scale, has produces some very nice effects sync'ed to MIDI, or to my playing style.
So – to answer your question – I've haven't been 'missing' that kind of feature, as much as trying to find a way to make it work. There are a lot of little features on other harmonizers that aren't *in* the PitchFactor. But I've never seen another stompbox pull off the *variety* of quality effects that the PitchFactor does.