Dear Henry, I just stumbled upon this revival of your interesting thread. I think in your post of March 6 you have accomplished a well known rhetorical ploy; you've raised a "red herring". My argument (and Dover's) was never primarily about plane parallel mounting of tonearm with respect to the platter surface, although I would never argue that this is not important. My argument for a fixed relationship and a physical connection between the tonearm base and the turntable bearing assembly had mostly to do with preventing motion of one relative to the other in response to external or internal sources of vibrational energy. One wants the combined structure to dissipate mechanical energy as a unit. My metaphor about trying to cut a diamond resting in a rowboat whilst sitting in a second rowboat vs performing the same task while having the whole operation in one boat (easier, obviously) was meant to illustrate the point. That's the "bad thing" that I fear could come into play when a tonearm is mounted on an entirely separate support system and dissociated from the platter/bearing. Disparate vibrations of the platter vs the tonearm generate spurious signals from the cartridge.
I would also posit that the problem of "parallelism" (for want of a better single phrase) exists for both types of systems. A less than astute user of an outboard arm pod could screw up the parallel relationship between tonearm bearings and LP surface even moreso than could a poorly executed turntable design. As someone else with a lot of experience in tonearm design once remarked regarding azimuth adjustable tonearms, having the capacity to adjust azimuth endows one with the capacity to really mess up azimuth adjustment, as well as to get it right.
