At the weekend I was playing some Farm Simulator, I didn't do much as the lack of Force-Feedback was disappointing but it did make me think of something.
Imagine that a player in Farm Simulator could sell their crop, at a slightly higher value than the local markets, to players in Eurotruck/American Truck. They'd be paid immediately (thereby removing any chances of being griefed) at a slightly higher value than the local markets. It wouldn't matter what map you're on, the only thing that would matter is that it would become available within the game world of Euro/American Truck simulator with the same "type" (e.g. logs/produce/etc..)
Just as with selling being a slightly higher value, the jobs that World of Trucks creates would be slightly higher also. To encourage players to indulge with the mission types. The game can still ensure that they are sourced from proper depots and delivered to depots that would receive the goods.
Why? I think it would be fun that players would get slightly higher payouts, achievements, and both companies would get good metrics about who took part in this kind of thing. I'd definitely do it!