Full trade ability will probably come later when freighters become available. The trading goods are already in place (clothing from Tau, mushrooms from Moison, phosphorus from Daedalus,... etc.). I personally would like to see a system similar to the old railroad board games where you pick up a load at one station (ship size determines maximum number of loads) and take it to whoever is offering the most for a load. Your idea would be a good way to ease into full trade, because your load is provided by the Side Job, as is the destination. Discreet Work would be the shadier side of the trade market where you are asked to obtain something from someone and take it to someone else at another station. Higher reward tasks should include a certain element of risk, as some things may not be exactly legal. I would treat them as a career task with an element of risk, which could result in injury, brig time, having your ship impounded, or even death.