Interesting thoughts...

I had to look further to see where modern cars place this intake port. I know my Honda has a tightly screed on cap with an o-ring for adding oil. Looks like modern cars place the intake inside of the air filter. I would assume it as after the paper filter element and this provides particle free air.

Doesn't help us unless you want an ugly cobble job.

I feel safe assuming the coarse mesh filter that is inside of the current oil filler cap becomes saturated with oil vapor and captures dust. Their is the small area where the cap presses onto the stem that is not sealed perfectly so some unfiltered air may get in that way. Maybe there is a way to get an o-ring in there to provide a tighter seal.

Good or bad, when I change engine oil I also squirt carb cleaner in the removed cap and shake it out to clean the filtering material. Maybe I should be leaving that oil in there to offer better dust capture.

I can think of another disadvantage to the paper filter you show. You would need a screwdriver to loosen the clamp when adding engine oil.

My current engine has the draft tube but still needs the intake type cap. According to the wiki page, this draft tube does not work at slow speeds as the tip of the tube, placed in the vehicles slip stream, does not provide the required vacuum., a problem for mail vehicles and us city dwellers. Interestingly the PCV system was developed during WWII for tanks which never get to a speed where a slipstream is created. Then the government got involved and now we can all breath easier

https://en.m.wikipedia.org/wiki/Cran...ilation_system