CarPlay and Android Car don't help you very much: They require a phone to operate. If you don't have one you get nothing. That doesn't sound like a big issue no

CarPlay and Android Car don't help you very much: They require a phone to operate. If you don't have one you get nothing. That doesn't sound like a big issue now but keep in mind that car multimedia is in development for about 4 years and then the cars are in the market >= 15years. This means if you now start to design a system around CarPlay you would need a iphone that supports the current CarPlay protocol in 2034. That's very unlikely. And when you don't have one you get nothing at all, neither music nor navigation. Directly building a system on top of android instead of QNX or a custom linux distribution is certainly possible. Every approach here has some pros and cons. Keep in mind that not all of android is open source and available for everyone. You can't directly use a normal Android phone UI because it is not certified for in-car use (driver distraction regulations). But you could at least use it's UI framework and some of the widgets. For the widgets there is the question if you want them. If they started development 3-4 years ago and based on android you would now get a brand new Ford with a Android 2.3 UI. Wouldn't look sexy either and even less in some years from now. Therefore going with some custom UI can make sense.