Automotive doesn't work like that. GM, for example, insists that if a supplier's part causes a recall, the supplier is responsible for the costs of the recall.[2] Auto manufacturers demand the right to send their inspectors into a supplier's plant. If supplier quality slips, the oversight becomes tougher. It has to be that way; a car has thousands of suppliers, many of whom can make the final product defective.
The new head of Google's self-driving project is a car guy from Hyundai. He understands this. Google now has a center in Novi, MI where 100 self-driving mini-vans are being built in a joint venture with Fiat Chrysler. That's step 1.
This is more of a management ego problem than a technical problem. Selling self-driving technology as an auto parts supplier doesn't fit with the "change the world" mentality. The automaker gets all the credit. Few people know the names of the major Tier I automotive suppliers. Microsoft ran into this once. Microsoft wanted the Microsoft logo to appear when the dashboard display booted up. They were insistent about this. The automaker involved went with QNX instead.
[1] https://cloud.google.com/compute/sla [2] http://gmauthority.com/blog/2013/08/general-motors-adopts-ne...