About revising responsibility structure
These are just ideas on how to rethink the game, Civ is so complex so multiple of options are open.
I think the only way to strengthen governors and mayors beyond simply limiting cities to 5, is to make these positions more meaningful. We need to make a Council of Governors (Senate), a Council of Mayors (House of Lords) and a council of citizens (Parliament/Congress). I also do believe we should split the military into several generals, like Rome divided its military into various formations.
The military is bound to remain weak unless we do the same thing to the military as we did with domestic. We need competing/cooperating military formations/armies and allow for the citizens to have complete competing long term plans for various scenarios. We should radically rethink the roles of the Domestic and the military, split their powers, and integrate FA/Trade and Science/Culture. WE could also group positions by buildings, so only the military could authorize a barracks and city walls, culture/science could authorize temple/colloseum builds. Workers should be limited to a 50 Worker challenge, so our infrastructure does not grow too fast and that the worker discussion get more meaning (saving DP, limiting growth and make worker discussions more important). A similar Cap can be applied to the military, having various caps for ancient, medieval, industrial and modern.
However, a 5CC would severely reduce the game into a micromanagement feast, where city tile managers would have everything to say and the rest listen. tile management is a critical part of CIV, but in a DG setting would reduce interest.
No adopted cities, maybe no adopted units and so on. If we could somehow link ownership of for example gems in a province and wine in another to trade deals, and for example the gem governor wants the trade deal above the wine governor, we could link the value of that particular trade deal to allowed gold rushes for that governor.
The same applies to workers, we could have a maximum of 10 workers per province, which would force the governors to think through where to improve. In general, we need to expand governors running build queues to also decide on workers in their province. A governor could later on trade a worker to another province for gold, trade privileges and so on. This would also create a dynamic in inter-governor relationships, as they need to cooperate/compete in the same time. They would need to address workers, land improvements including fortresses, irrigation and mining as well as land clearance, buildqueues, now authorized by the military or science/culture. Additionally, these would get direct benefits from the trade deals, so leading a resource rich province would create many potential rushes.
Governor
Control up to 10 workers for the province
Build queues in cooperation with ministers and mayors
Decide on Province infrastructure and tile improvements
get 40-70 % of the Gold from trade deals coming from resources traded from province used for rushes.
Governors may authorize wonder builds in their province
Finance Minister
Market Place, Bank
tax slider, control national treasury, (takes tax of 30-60 % of trade deals)
Culture/Science Minister
Temple, Library, Colloseum, University
propose areas where wonders could influence borders, but not wonders themselves
propose research of new sciences
request scientists and entertainers in cities from governors and mayors
Military Minister
Barracks, City Walls
request police units
FA/Trade
Harbor, Airport
Domestic Minister
Settlers, Granary
Justice Minister
Courthouses (Also request Police units)
Police stations, Espionage actions
Watch corruption levels
handle Forbidden Palace, Mobilization, regime change
For the President, I would propose to hand over the responsibility of wonders, as heads of states often made those decisions, and take away the workers.