I heard that one of the Chinese car companies was taking that approach with some of their cheapest models: people already have phones, just provide a nice place on the dashboard to hang their phone, just provide an ordinary Bluetooth speaker as the sound system, and just provide a Bluetooth app to control some of the car's lesser used functionality like the most detailed parts of the climate system and what have you.
It's a fascinating approach. I don't know if it would take off beyond the smallest, cheapest types of cars, and I certainly don't know if we'll see those sorts of ultra-cheap cars in markets like the US, but it's still great to hear that some experimentation is going on knowing that everyone already has smart phones, modern cars are an extension of that (look at the importance of Apple CarPlay [1] and Android Auto), and there's a lot of room to experiment with an electric car (given how much of an electric car is a "software car").
[1] Fun semi-related footnote: on the highest end, as well, Porsche was getting some good press that they'd moved a bunch of their controls into an iOS app that supported CarPlay. Porsche seems to have perhaps realized that "CarPlay" is the real car OS most users care about.