not fitted one to a car yet but given the amount of stuff that gets put back into the manifold in the name of emissions reduction I can see myself doing one soon - I was looking to adopt the same simple method used on my bikes. Have the vents going to the catch tank only with the tank venting to atmosphere - mounted away from the air intake to the cabin. The oil gets retained and the pressure gets vented to atmosphere.
The intake system on the car now just has external air and petrol going to the cylinder heads
wrt points 1-4 above
1) what benefit? Also the positive pressure generated in normal engine operation circulates air no problem
2) so is the current industrial revolution happening in China plus cows farting
3) never had that using a catch tank with filter attached to the vent and an internal baffle
4) If you blank the feeds into the manifold and turbo inlet this becomes irrelevant - although Im not convinced of its relevance in its own right.
I would start with a simple solution - even if it means two catch tanks to reduce plumbing, blank the intakes and remove the PCV