Making other commodities would put a huge strain on the system as is I'd think. Since there are so many stations, each of them has a price for each and every commodity. That is a lot of price settings you've got to do to implement each one.
With this, its my theory that a mission be placed in certain 'productive' stations, like prisons, factories and shipyards etc etc The player needs to take the goods to their contracted buyers, and make some money. Via the contract mission and any cargo they wish to take if they can fit anymore.
Sure piracy may hinder the missions, but that is the idea. It gives new players a jump into the piracy avoidance rather than go "Why you stop me?" syndrome to newbies. Maybe in the mission description it tells your the dangers of piracy?
These are meant to be jump starts for newbies, but it can be used as a RP way to rep up with a company without bribes and killing things, making it more immersive and logical.
Still hoping this is possible and that Cannon reads his mail... I hope he luvs me...