Its true that the electronics gets really overwhelming these days. But the base principle should be of STANDARDIZATION as in the IT industry and the Telecom industry. With standardization, things gets more ordered , cheaper and more relaible in the long run.
Unfortunately, the automotive industry has been a highly proprietary one and will remain so for a long time. Its electronics is getting "opened" up by standards such as the CAN bus. In an E39 and onwards model, there is CAN bs, i-bus K-bus. so many electronic buses in the tiring to do the ancillary things to keep things like audio, sat-nav, TV,alarm, etc keeps us entertained in the car. The primary ECU or DME runs in a failrly closed system, which is good.
With regards to Audio even CD change bus are propreitary like Alpine's AI-net which is a good system I believe. Customers want to mix and match their audio equipment like the mid-end to high-end components you use at home.
The problem with car manufacturers trying to package the best compromise to the customer is a novel thing but please please, give the customers a choice!. These days customers are so much smarter than the manufacturers think so it is pointless to try and get people to use their packages items, if people can choose others.
Example, most people upon buying a Japanese car, start to change to rims and tires. So you ask yourself and the manufacturer, why not sell the car without rims and tires ?.
For audio in BMWs, Blaupunkt has higher-end OEM replacement audio components, as your authorized Blaupunk dealer about this.