Honch, it seems to me that you might be able to do that in the Phaser algo now. I don't have that algorithm yet, but perhaps using the sample & hold waveform with one of the deeper phaser types.
I did something similar with filters in the PitchFactor's HarPeggiator algo, and it's one of my favorite presets. I still have my SE-50 here [sadly, no MIDI sync rate]. I'll need to compare that with the H9 offerings to refresh my memory. I remember a Stereo Flanger effect with Gate on the SE-50, but not the Step Phaser.