In thread about pace coments problem with massive districts in cities with enormous passive income. I see trhee ways to solve this problem;

1. Stability: Increase stability malus with every new district, maybe necessary for city growth in the late game a stability worker (police, politicians?). With this could be more difficult build district massive.
2. If you don't fill all worker spaces reduce passive income of this type. farmer are useleess only with passive income in other way. With more district more workers space and if you control pace growth population could control passive income in district.
3. Nerf bonus. Some district passive income is enormous with all bonus applied

On your first idea: there was an option to have stability workers in the previous OpenDev. The removal of it as a feature is probably due to criticism about Stability then and has potentially been ruled out as a solution internally.