I think you will be generally ok without ducting until you are running R-comp tires. If you are running R-comps and run many consecutive hot laps, then ducting will definitely help. In my case when I was unable to run more than a few consecutive hot laps due to brake pad fading and also engine temps creeping up. I never installed brake ducting on my car as it generally causes trouble at full steering lock for a car that is daily driven.
Have a look at some examples in
this thread
Don't bother with BMW performance brakes as the rotor is the same size.
If looking for an OE style upgrade, maybe consider the F22 M235i 4 piston calipers with the larger discs. A few people have done this swap.