I think it would be cool if we had more to do with the car editor. I know you can now slam pretty much any car and put obnoxious tires on it but I want to do it the other way around. I want a way we can lift cars to a crazy height and put massive tires on it, such as lifting the Pessima and putting the Offroad D15 wheels on it, to result in an offroad Pessima. I already found how to do this at the thread link below, but with the newer vehicle modifier and all the new wheels for cars it would be nice if it was easier to make these monstrousities. Just look at some of these terrible and amazing cars people made with my idea: http://beamng.com/threads/insane-vehicle-modding-in-game-d-i-y-guide.16418/page-2#post-301366
Would also be nice to equip insane amounts of camber so you can drift and then destroy your cancerous car.
You can already put stance-level cancerous amounts of negative camber on the car, any more and you'd need special suspension components to allow that sort of geometry. The "tuning" allows you adjust the car in a way that such race components could: IRL, you can't twist a coilover until you get a 15 inch lift.