then you will just vent the crankcase gasses out to the atmostspere, "I wouldn't recomend it" the crankcase gasses are routed back into the intake manifold to be run through the combustion chamber again and out the tail pipe. Diesels require a slight vaccum in the crankcase.
The cdrv is there to regulate the vaccum. For example next time you have the engine running take the oil cap off and notice the white smoke, if you stuck a filter on it all that smoke would just pile up under the hood. Unless you want to be that hoop dee rolling down the street smoking like crazy!!