No, a software switch is not enough. We need to be able to physically unplug the cellular modem entirely and have the vehicle work with 100% functionality (barring features which inherently require cellular connectivity like turning the heating on remotely)
Car manufacturers' features are mostly useless anyway thanks to Android Auto/Apple CarPlay
Just for AI image generation i would rather recommend krita with the https://github.com/Acly/krita-ai-diffusion plugin.