Sodell, you are right about the V8 being able to pull the fresh air into one valve cover and the dirty air and moisture out the other side. That is the ideal situation, but not very practical for an inline engine. There are a few 4 cylinder engines with the PCV plumbed directly to the crankcase, but they are designed with baffles to keep the oil out and the air flowing.
The Chevy designed system of having fresh, filtered air from the air cleaner, enter the valve cover at the front and rear exit through the PCV valve to the intake manifold works quite well.
At the end of the day, a system that included a crankcase entry point would not keep the engine cleaner, provide cleaner emissions or longer engine life. You would just have a more cluttered looking engine.
I have never cared for the breater caps. They have a cheesy, cheap wire mesh inside that are impossible to clean. Fresh air from the air cleaner means when you clean or replace the air cleaner element, you are covering the PCV filtration as well.
