The ability to add cargo of varying weight to vehicles. Such as boxes in the box van, or for the back of a semi. I essentially would like to be able to pick a vehicle like the van or the semi with box trailer, hit the mod button in-game and add some cargo to the back in it. The cargo would be tied down so it wouldn't flop about in the back. I've always wanted to go through a bumpy trail with a D15 loaded with logs or something, or watch the Vanster suspension struggle with a huge load in the back while trying to get up a hill. Either preset cargo models with different weights, or the ability to add a box and select how heavy it is. I've tried adding vehicles to the back of trailers and such, but they never stick in place, even turning slowly causes the vehicles to slide a tiny bit and eventually they will fall off. There's no way to tie them down (parking brake isn't sufficient). If there is, I guess I missed that memo. Anyways that's it. Would be awesome to see some day. For now I have the concrete semi which is holding me over till that day comes! I did do a search to see if this was previously asked, perhaps I just didn't use the right terms but I didn't see it suggested.
There are a couple mods that have tied down cargo options. http://www.beamng.com/threads/gavril-d15-d25-d35-stepside-etc-v0-5-1.6538/ http://www.beamng.com/resources/gavril-h-series-addon-mod.65/