One thing I've noticed when playing around with zones is that Buildings generally being flat job bonuses does add a lot of little oddities. For example, building one of each rural district adds a lot more jobs on a planet via the relevant buildings, while building an Industrial District means that your consumer goods and alloys will slowly even out towards 50-50 the more you build. Additionally, not being able to preview which buildings a zone can produce can feel a little odd.
I think that adding jobs-from-districts to buildings, and ensuring Urban zones can build all building types, would address a lot of issues discussed. For example, if an Alloys building adds something like +50 jobs and +25 jobs per district, then an Industrial Zone with 2 alloy buildings and 1 consumer building would converge towards 1 third consumer goods and 2 thirds alloys. Urban zones that can access any building would then act as a means of fine-tuning your planet's production ratios, with the opportunity costs of getting generic clerks instead of base zone jobs being the reason to specialise- this would make the early-game or single-planet games significantly easier to wield, as you can scale a small amount of up to 16 jobs (3 per government/urban zone plus clerks, 3 rural) instead of only scaling a large amount of 6 job types (3 urban, 3 rural) per planet.
