It would probably take more power run a pump than it would give you in fuel savings. A slight vacuum will help stop oil leaks, but, wants to pull dirt in through the same leaks. Pressure will help oil leaks become worse. The CDR is an attempt to keep the vacuum under control so the engine oil consumption is not as bad along with other things - just the air filter alone is too much vacuum with good rings.
The downpipe has pressure due to the muffler, cat, and total length of exhaust pipe.
The CRD routed to the intake lets the engine burn a lot of the 'mess'. We don't have an intercooler and I don't have EGR. The oil that does go through the CDR helps keep the intake clean on the inside. As for the outside... No.
Some of the modern diesel oil stinks in use due to additives to meet the newest requirements. So a intake CDR system has a odor control advantage. My trucks smell bad enough without additional help from more odor sources under the hood.