Actually the Peel P50 would be theoretically one of the easiest cars to make a mod with scratch made Jbeam of. Why? Because when you order this car nowadays, you have an option to order it as a building kit with all the parts so you can build it yourself. It's very simple and doesn't have many parts (for car standards of course). You could buy the kit and start building, but each part you could check the exact weight of, and make a 3D scan into Blender of it, Jbeam it and put in game. You would build it irl and in game at the same time. You could check stuff like spring stiffness and shock damping on the real parts precisely before they go into the car. I think I have explained this enough, that would be so cool to do. I would do it myself if I had all the stuff needed for it such as garage space and a 3D scanner.
It was made many years ago back when they were allowed I guess. You can find some really bad mods from that time period, most of them being jokes but there are also serious mods that are bad because they are low effort.