Tonearm mount to the plinth vs arm board vs rotating arm board vs isolated tower

I agree with @halcro , it is essential to isolate the tonearm from the platter bearing and the motor.

This opens the turntable to colorations. Apparently Thorens has this sorted out:

The idea if I understood Greg correctly is that everything vibrating is concert is better than vibrating out of synch.

This is why the tonearm must be rigidly coupled to the platter bearing, and hopefully the surface of the platter as a result.

Nandric
Those who intend to build an new plinth for their TT's are in different
position from those who want to keep their TT as is.

@nandric 

Nikola
With these old idlers, (Garrard/Lenco's, etc...) like the OP of this thread is considering rebuilding ... everyone I know .......from the past, current, and I presume anyone on this AudioGon site, is not using this turntable type (idler)........ as is.

Buyers initially seek out the motor/platter system.

And....even then...... many folks, as in the case of the Jean Nantais Lenco version I ended up with; have replaced or significantly modified the platter, top plate, put in a new idler wheel, Spindle, thrust pad, bearing, etc.....

The finished tables people discuss on these audio sites bear very little resemblance to the originals.

@fsonicsmith , sorry to offend you. I was merely attempting to contribute to the discussion by suggesting that these desired characteristics could be obtained without (much) compromise, in part by finessing the problem, and partly by choice of materials. On re-reading my post, I realize that I was imprecise. I could cure this, but it might be tedious. Incidentally, baltic birch is a poor substitute for panzerholz. Ask me how I know.

@atmasphere , my imprecision obviously bothered you as well. I was trying to express the idea that an air bearing could be made silent, and so finesse the problem of transmitting platter bearing noise to the tonearm. I agree about a rigid coupling, which is incorporated into the design.

Dear ct, my first dispute in this forum was with Lew and regarding
Lenco platter. I was sceptical about possibilty to make a better one
in someone's garage or cellar. But my point was ''don't mess with
your TT''. His answer was : ''Nandric messing  with TT's is fun''. 
I was ''speechless'' . 

^^^^
It's very easy to mess with a used turntable that cost a couple hundred dollars to acquire.