I am not an engineer but it seems to me that a light car should be able to be propelled for short trips by human power. I suggest a bicycle drive connected to a hydraulic pump that in turn feeds an orbit motor or perhaps directly to an automatic transmission. I suggest hydraulic power rather than mechanical drive because a relatively small hydraulic pump can produce tremendous pressure. Heat from the oil flow could be cooled through the existing oil cooler or directed to an interior heater for cold climates.
It likely could not develop highway speeds but most urban traffic now flows at less than 60km/hour. For longer trips perhaps it could be supplemented with a small gasoline engine similar to those used on bicycles occasionally.
I welcome advice or suggestions.