Hi Joe,
How I read the oil flow diagram is thusly:
oil pan -> oil strainer -> oil pump rotor -> oil cooler -> oil (filter) element -> Cylinder block main gallery RH -> #1, #3 cylinder head RH -> oil pipe -> Turbocharger -> oil pan
It seems that the oil has a long way to go, but it doesn't really go "through" anything in the same way that, for example, the #1 connecting rod bearing gets oil that has hit the #1 journal bearing (front) first. That was my reasoning that the oil wouldn't pick up much cruft on the way. Does that make sense?
As for an inline filter, you would probably have to replace the oil pipe that feeds the AVCS and the turbo with flex hose with the proper fittings to install the hose back onto the turbo and AVCS solenoid. Doable, but you might be better served by running synthetic oil and/or a bypass filter.
-Ryan