"The tonearm is now the centre of this Turntable System and is the most important element. It must be rigidly held on a base which is perfectly flat, non-magnetic and relatively immune to structure-borne and air-borne feedback. This base must ideally have no contact with mechanical or electrical interference and must under no circumstances, move or deflect in any manner.
This base should ideally have no contact with the drive mechanism of the platter or the plinth, sub-platter, belt, gears, idler-wheels etc.
This base should be an island."
What a vacuous discussion. Suggest if you believe this, then sell your turntable, motor and records and just listen to your arm.
Your statements above contradict themselves - for ultimate speed speed stability there must be no movement between the drive and the platter. For ultimate generation of music from the interaction of the stylus on the record, then there must be no movement between the arm mounting and platter.
Ergo the motor drive, platter, arm and cartridge must be coupled together in a closed loop system that is absolutely rigid and yet has no transfer of unwanted energy between them that smears the speed sound or whatever.
In fact there should be no cantilever suspension to ensure as much transfer of the signal as possible - much like a rally car where they remove all the rubber mounts in for the engine, gearbox, drive etc to maximise power to the ground.