The roof rails are a fashion trend used in a practical way by very few. In Europe, the identically specced Niro (same cooling system and brakes) can tow 750 kg without any towing package. Mind you, the trailer is supposed to have brakes, but a trailer without brakes the size of a rooftop box is not going to cause an issue. When I hear camping, I think long trip and no access to plugging in. Under such conditions, the PHEV will be getting less than 50 mpg. A rooftop box is going to cost at least 5 mpg on top of the hit the roof rails already have. But it is not my money, and lifestyle choices usually win over economy anyway.
2018 Kia LX HEV Metal Stream with Advanced Tech