I think a U-Haul trailer or a caravan with opening doors would be nice. It would improve realism and be more fun in general. maybe even a U-Haul skin on the back of the Cabster's box. I can't make mods, this is just a suggestion for someone like Bernd, because he makes little knickknacks like something like this.
Plus I think the trailer it sits on would be an amazing car trailer. I hooked up the Pigeon Sti-G and hauled it around, having the size of the Pigeon Sti-G right in front of the trailer showed how well it is on size, I think someone needs to convert it over to just a trailer with a ramp in the back.