newtuner, the 2nd to last picture you posted doesn't work and I am kind of curious about seeing it.
You said you planned on rebuilding your original starter. Is it just the carbon brushes that need replacing or is the commutator done as well? Does BMW even sell these parts? Just curous....
I had my starter replaced while I was under warranty. My symptom was a loud squeal for about a second right at startup. It would only do it when the motor was cold and it was more prone to occurring if the ambient temp. was colder.