Exactly. How about a self-sustaining eco-system for his new world? Or biodiversity? Or - as long as I'm throwing terms around - how about the butterfly effect? Yes, Darhk managed to grow corn that apparently can create an oxygen-rich atmosphere, but people need more than oxygen to survive.
Incidentally, at least two media reviewers asked the question of why Esrin Fortuna didn't turn to Felicity next, after Oliver failed his test - since she usually brings the light. I'm guessing, it's because: one, Oliver has the magic tattoo, and two, it's Oliver's show.