I would like to see the Gravil D series with a Diesel Engine and some stacks too. That way you show up to town and be like what up and just start rolling coal like this. I would love to do that in Beamng drive since I know I most likely won't roll coal in real life. Same thing goes for the semi truck as to be able to have smoke coming out of the exhaust. Also would like a 6X6 automobile such as this. That would be so much fun to play around with. The 6X6 could be made off the Gravil D Series. It could be called the Gravil 6X6 or something like that.
I'm not sure about stacks but I believe a diesel is planned for the D-Series. As for the the 6x6 somebody has already made a mod for that here.