DP would work fine as the only time we see positive crank case pressure is under boost when the wg is likely to be open and flowing.
This is not a new idea. works well.kinda sooty for a street car tho.

 

That unfortunately is not the case. Unless you sit at idle all the time you do build up crank case pressure even when cruising. I used to see this often when I would just dump the breather box vent right to the ground and use a small filter on my valve cover. My oil pressure would start to climb until it hit the limit and then drop when I got on it to "push" the pressure out the vents. Honda's for the most part just don't have enough ports throughout the block and valve cover to let it breathe without a vacuum source...or at least breathe well.