There are obviously going to be two different trains of thought here. Personally if I owned a classic car I'd want it to be the spec it was originally. If I want the comfort of iDrive then I'll get in my 530i.
Alright, IDrive is going too far, but stuff like uprated brakes, suspension, a tad more power, etc would be a welcome addition.
Times have changed and old cars can be improved on.