> What would be difficult is quantifying note attack exactly for XYZ's riff sections.

At 60 BPM, mathematical quarter notes are 1000ms apart. But in a pocket groove, you may notice that every other quarter note is "late", or "swung":

  |o---o---o---o---|  (mathematical)
  |o----o--o----o--|  (swung)

Another factor that affects rhythm is note duration relative to the tempo -- you'll want to measure that too.

> Matching another guitarist's intonation down to a tee

I suspect if you study a few groovy songs you'll find there's just a slightly different note grid that's common to these songs (there could be more than one grid!) Teaching this grid (rather than teaching one specific song) will help the student learn to shift notes away from the the mathematical metronome placement. This skill will equip many of them to mimic the feel of their favorite artist by ear.

I see what you mean now. I interpreted note attack as pick attack, which is traditionally defined as how hard a given note is played with a pick.

Yeah, swing usually has uneven subdivisions. Funk is almost always syncopated, and depending on the style, can be a mix of syncopation and swing.

This goes back to how you noted simply using a metronome will give that mechanical, or even a soulless characteristic, to playing a piece which inherently has a soulful quality about it. And with respect to intonation, there's a lot more that goes into that than just timing it right (how hard fingers are pressed on the fretboard, the pressure between fingers holding the pick, the angle of the pick, where the pick strikes relative to pickups, the pick attack, accenting notes, etc.)

I do love this idea of being able to apply some "in the pocket"/"swing" deviation to a metronome sequence. I agree with you that it adds that magical musical quality that people would instinctively dance to.