[tongzilla]

I get the feeling that if one can achieve the Flat left wrist at impact the rest of the imperatives will fall into place with practice. Anyone else agree?

No, don't agree. Too many golfers out there with a 'fake' Flat Left Wrist (what the heck? ) at Impact.
Out of the Three Imperatives, if I really had to choose one where if you could do it everything else will fall into place, then I would choose Clubhead Lag Pressure.