Yet another example of car companies de-contenting to save a couple bucks, or in this case, euros.
I am not sure what the function of the panel is but I am going to venture and guess that it protects the bottom of the oil pan (with that thin plate ?) and makes better aerodynamics.
Anyhow, I will try to order it from my local dealer, Shelly's BMW.
"The most likely way for the world to be destroyed, most experts agree, is by accident. That's where we come in; we're computer professionals. We cause accidents." -- Nathaniel Borenstein