I am the driver and my weight is 70 kilo. In the front passenger seat is my bodyguard whose weight is 200 kilo, and behind him at the rear seat is his girlfriend weighing 150 kilo , and next to her, behind me is my girlfriend weighing 50 kilo, and in the trunk is Carlo 120 kilo, and we're going for a ride.
Who is Carlo? And why is he in the trunk Yeah I get what you mean, but it will be quite hard to implement various different things, like this is a car game not the Sims so it won't weigh things like fancy hats and etc. A simple weight in the car is easy tho, but it would he interesting going ovrr bumps if it was a thing because then the passengers would fly around which would make the car wobble
Carlo could be a guy you have to smuggle over a border, but then the border police sees you and you have to outrun them, in a uneven balanced car. He could also be a dead guy, you have to bury in the desert , or a big bag of money etc. The main thing here is the opportunity to add weight from the driver, passengers and cargo, as you wish, to experience how the car handle differently, in different weight scenarios.