The discussion is going on, but the my mainpoint is to make Engineers and Traders more like a team. So one of the mainpoints is to make traders and engineers more dependent on each other - but how can we do that?
Why should we make engineers and traders a team when they create things? In real world it's working like this:
1. The engineer invented/making a new item, the engineer don't have the knowledge to sell the item on their own (therefor traders got good buffs)
2. The trader take care of the marketing and buys the item of the engineer (because he can have better skills?)
3. Both traders and engineers have made a profit, and the customer is paying.
But today are traders forgetting all about the first step and make the things theirself. How can we avoid that? We can give engineers a small buffline that is half of traders but stack and is self-only? This way will both traders and engineers ask each other when they have to make a new item (you can also make the new buffline others too, but if you want to follow the model above the buff should be selfonly)