Air goes into the PCV system through the valve cover, so if it is filtered by a breather filter or the intake system, it is getting the same air at the same pressure.

You are thinking about the breather tank at the back of the engine block that has the PCV valve attached to it. The hose carries oil vapor in through the intake manifold to be burned. There is no way you could change that part of the system around since it is all dependent on manifold vacuum.

I am sure the breathers are illegal. For what reason, I don't know but if the politicians and lawmakers can find something to bitch about, they sure will, even if it has nothing to do with pollution.