My concern with Apple Car being just a software layer between the machine and the driver is one of safety.
Depending on the level of integration, how is Apple to to ensure that it doesn't over accelerate or indicate the correct speed? Or if it's an EV, that the battery isn't overheating?
I think it opens them to a whole lot liability if they're meant to interface or control core systems that enable the vehicle to operate and ensure the safety the occupants.
If it's just meant to be a fancy stereo then whatever I guess though vendor exclusivity could be a annoying. For example, BMW only interfaces with iPhones and Apple products so if you're an alternative platform user you'll want to find a different brand of vehicle. Just sounds like a headache.
