Better speakers is an easy add on. Power windows are probably uncontroversial. I don’t think there is wide demand for built in gps. I just don’t see the problem

Better speakers is an easy add on. Power windows are probably uncontroversial. I don’t think there is wide demand for built in gps. I just don’t see the problem you describe. Design a basic dumb car base that can be extended with addons. There may be regulatory and other non-necessary obstacles but the ideal seems widely agreeable.