With the new trailer connection system, more trailers for the T-Series would be nice. Possibilities: A car trailer like this. (Maybe not so large) A flatbed with loads that you can choose in the vehicle modification menu. A tanker trailer that can burst into flames from collision.
That amount of trailers and quite possibly even more, will surely be added in the future... When the devs figure out the right trailer(coupling) and game engine optimizations, it will be a lot easier for mid tier or (very unlikely) low tier PC's to handle all of that. But for now, it's just too hard for people to handle that in their game.
