Direct Drive vs. Idler Drive vs. Belt drive

Atmasphere, it is my understanding that a properly designed air bearing turntable is virtually as stiff as any solid bearing. The platters are very heavy and the air boundary is very thin on the order of microns. It is extremely compressed. Just the mass of the platter would make minute vertical movements impossible without rather extreme force. Having said all this I think it would be extremely difficult to hear the difference between and SME 30/12 and an Air Force One. But, the Air Force One is three times the price due to the added complexity and expense of machining opposing faces of the air bearing to such high tolerances. 
My own feeling is that it is complexity for complexity's sake.  

IMHO a properly designed Belt drive turntable such as the Sota Cosmos, the SME 30/12, and the Basis Debut are the best solution to this problem.
The problem with Direct Drives is a big oscillating magnetic device directly under a very sensitive magnetic device. With Idler Wheel tables it is the added mechanical complexity adding noise (rumble)   

I had Nottingham Spacedeck and moved to heavy plinth Lenco 78 with SME 3009mk2 tonearm.
Lenco won in term of PRaT, piano and organ tone, better bass, better instrument separation, more musical. No rumble.
And Lenco wasn’t expensive High End turntable it was mid budget turntable.
Belt drive like Nottingham kills rhythm nuances and plays separate sounds. The general picture of music the essence of interpretation itself is disappears.

Regards,
Alex.

Perhaps you should try a heavy platter NA. I have one, and it does not suffer from the ills which you list.

After Lenco I use EMT 948.
It is a number of levels over Lenco and Nottingham Spacedeck.

Other my friend audiophile and musicant (flute player solist and conservatorio teacher) 
threw away his heavy platter Sota turntable after buying EMT 950 DD turntable.

@chakster, thanks for the picture of the two samples of CU-180. I also have two samples with similar differences. I've always wondered if the one with the 'deep groove' was the original, like my blue note pressings! But in this case they sound the same....