I think you misunderstood how I'd use the b22. I would use the opamps in unity gain (or maybe 2x) to create the OG/OL/OR, then feed those three signals into three separate b22 boards to drive a headphone. Does anything seem wrong with that?
Along those same lines, are any opamps better at driving high impedance/line level inputs (ie: the b22 input impedance) rather than headphones which are comparatively low impedance? I think I've read in a couple spots that opamps work fairly well either way, but some perform better in that application than others.
If I do a full b22/s22 build, the s22 has a fourth output which I could use to power the "active balanced ground" circuit (maybe run it through a s25 transformer to bring it down if needed).