I've fallen behind in this thread, but have Adjacency Bonuses and Citizen Yields been addressed? Personally I feel like a failure if I build a District without at least a +2 Adjacency Bonus (or the anticipation that I can make it +2) and I think it can go as high as +5. Harbors provide Production with Shipyards, in the form of an Adjacency Bonus. I think the Citizen Yield for an Encampment is +1 Production and +1 Culture, where it's +2 Production for Industrial Zones. Military Academies and Seaports can also provide a +1 Science, but that requires a Social Policy card, so I'm not convinced that's worth it.