If I weren't sure that car makers would botch the security, I'd be in favor of legislation that requires that for a specified list of controls or categories of controls if the car does not provide dedicated physical controls for them (either solely or in addition to non-dedicated controls) the car must also must provide an API for those controls to allow third-party add-on devices to operate them.
The API and how it as accessed (e.g., OBD port, Bluetooth, USB-C) would be specified, along with an extension mechanism to allow car makers to optionally allow more than just the required things to be controlled in a way that wouldn't conflict with extensions from other makers.
Then go ahead and go full touchscreen if they want. I'll buy a nice third party set of controls and use that with the car, and since the API and interface is standardized I can move it to my next car and so on, and so not have to learn a new layout for each car.
I say "non-dedicated controls" above instead of "touchscreen" so that a manufacturer can't do something like have a knob and a couple buttons coupled with a screen where you use the screen (via touch or using the knob and buttons to navigate) to choose a set of functions from a menu tree, and then activate/adjust those settings with the knob and buttons, and say that they don't need to provide the interface and API because they are using physical controls.
The API and how it as accessed (e.g., OBD port, Bluetooth, USB-C) would be specified, along with an extension mechanism to allow car makers to optionally allow more than just the required things to be controlled in a way that wouldn't conflict with extensions from other makers.
Then go ahead and go full touchscreen if they want. I'll buy a nice third party set of controls and use that with the car, and since the API and interface is standardized I can move it to my next car and so on, and so not have to learn a new layout for each car.
I say "non-dedicated controls" above instead of "touchscreen" so that a manufacturer can't do something like have a knob and a couple buttons coupled with a screen where you use the screen (via touch or using the knob and buttons to navigate) to choose a set of functions from a menu tree, and then activate/adjust those settings with the knob and buttons, and say that they don't need to provide the interface and API because they are using physical controls.