Sophisticated Redneck - I went with my plumbing configuration based on other engines that I've seen vented this way, but I will continue to monitor the oil use. My E39 M5 factory PCV system vents the crankcase breathers into the intake tract before the throttles so it would be similar to how I plumbed this. At low loads there shouldn't be much blowby and really the crankcase vapors just need somewhere to go, not much pressure differential is required. At high loads, crankcase pressure rises and the turbo suction pressure should drop due to dp over the air filters and the crankcase pressure should remain nominally neutral. More time is required to see if my solution is adequate.
Thanks for the tip on the rain deflector, I will pull that off to help things out under the hood.
RichardH - For the engine thermostat, I used this:
https://www.bmwlogicseven.com/?tag=n63 and for the oil thermostat I used this:
https://n63intake.com/product/n63-n6...-cooler-valve/. The first few times I ran the car afterwards I would get codes for the engine temperature being too low at shutdown and off the cooldown curve the ECU expects but the ECU seems to have adapted to the new setup and I don't get anymore faults now.
The coolant temp stays around 90C now and the oil temperature is slightly higher. As documented elsewhere, the factory oil temp gauge lies (indicates colder than actual) and now the needle sits a bit to the left. Actual oil temperatures run around 95C.