I've thought of this while playing. After smuggles, smugglers can be rewarded with coca seeds, which can be grown in the drug island. After the plant is ripe, players can /harvest it to gather the plants. After that, they can proceed it in the Drug Factory in order to make it become real cocaine using the cmd /proceed.
Also:
- the grow time shall be the same as weed seeds
- the amount of cocaine that can be proceed should be smaller than the number of seeds as in real life (no idea on this one)