CarPlay integration is a feature bundled into the infotainment in many cars that requires an "external network connection". It will not work if you disable the "external network connection".
What if I want to control (e.g. close) the garage door when I am out of Wifi range?
Whatever the case, my point is that a good solution is probably not quite as simple as phrased above.
And either way -- just keep supporting connection over USB and it's not a problem?
https://support.apple.com/en-us/HT205634
>If your car supports only wireless CarPlay ...