Vintage DD turntables. Are we living dangerously?

Dover,
Your "rules" apply to belt drive tables and seem inappropriate here. How is a DD motor mounted on a separate platform? Using a plinth or subchassis does not necessarily maintain mounting distance better than separate pods.
Regards,

Thuchan,
I was thinking a cantilevered armboard would have greater potential to resonate, but maybe that too would depend on execution.

Free floating pods? I think the pods would have to be coupled in some way. If by free floating you mean mass coupled, that would be possible, but difficult to execute. If you eliminate the plinth/subchassis, then the mounting surface becomes the means of closing the loop. Pods could also be rigidly coupled.
Regards,

Dear Lewm,
that seems to be a brilliant idea: why not building a massive slate plinth, let the 101 sink in the middle and Henry`s pods at three other holes having rigid contact with the slate plinth. will draw a draft.

Dear Fleib,
okay - that makes sense! I could build up a round aluminum (or using other material!?) corpus in which the 101 sinks in keeping rigid contact. Three floating but rigidly coupled armbases -eventually not neccessarily flying in the air- keep contact with the corpus via two massive tubes like at the Feickert Triple. The armpods will carry a flexible upper level segment which can be exchanged like at Henry`s pods.
This upper level plate will also carry a flexible & fast changing system as it is implemented at the Firebird thus enabling using 12, 10 and 9 inch arms.

This design could fulfill the rigid contact requirements of arms, motor and platter. The main issue will be that the 101 keeps contact with that "kind of plinth" as you suggest.
regards

Thuchan,
A DD affords possibilities not available to BD and suspended, and when looking at the complete design I think you should also consider other aspects. Energy dissipation is of paramount importance.
J Carr tells us that only a very small percentage of cart mechanical energy is used by the generator. The rest goes into the cart body, headshell, then travels down the arm. Some of it will be absorbed (converted) by the mass of the counterweight and arm structure. Then it goes into the plinth/subchassis or is dissipated to the mounting base.

Just as a plinth can convert or transmit cart mechanical energy, it can transmit motor or acoustic energy to the arm. Doing away with plinth/chassis does not entirely free you from this consideration. A mounting base could potentially do the same.
Slate happens to be good at transmitting vibrations. I suspect its successful use in tables like Saskia, is due to its weight. That table weighs 200 lbs. but I don't know much else about its construction. Mass/weight tends to convert mechanical energy to heat. Which brings us to your 101 pod. Steel is much heavier than aluminum, almost 3X for the same volume, and brass is heavier yet. Lead is even heavier and is very good at slowing vibrations. In the past it was used in tables and speakers in combination with other materials.

Feickert Triple uses two steel(?) bars on each pod connecting them to the platter base. He also has some kind of anti-resonance circuit. Without his testing capability it might be better/easier without the connecting rods? You could plant the pods at locations convenient for different length arms and still use armboards.
Regards,