My advice is to insulate and seal that shed up. It's likely that you will encounter pests otherwise. I don't see you controlling the environment in there unless it's sealed and insulated.
As to ventilation, it might solve the problem when the air outside is cool and dry. But when it's hot and or humid then your makeup air that comes in to replace exhausted air, will cause more problems.
If it were me and I was forced to grow in a shed, I would first seal it up like a drum, pour a pad and spray foam it. Before that I would make sure I have trenched in the utilities I require. Then I would run it sealed with CO2, AC and deuhmidifier.