Your in-car software's architecture should by no means put "the part that is critical to driving the car safely" and "the part that runs the entertainment syste

Your in-car software's architecture should by no means put "the part that is critical to driving the car safely" and "the part that runs the entertainment system and heated seats" anywhere near each other. If they are, your design is braindead and unsafe. If they are properly separated, modifying heated seats is a non-issue.