Peaceful capture
I wish the devs introduce a peaceful way to take over cities, e.g. by triggering an election in a foreign city. For instance, a happy city may trigger an election in an unhappy foreign city bordering it, because people would rather join a happier, more affluent country. Or a city could have ideological differences with its country and join you or declare independence. For example, the city is Catholic and the country declares war on Catholic's founding country.
Tile flip
Next suggestion is tile flip across borders when your culture is stronger. In this way, you could take over some Wonders and nice districts, instead of having to pillage your enemies every time or take over the entire city.
Golden ages
Not all golden ages are the same. We could have military golden age where we can build military units faster and they promote more easily. We could also have golden ages of different types like cultural, economic, diplomatic, religious, etc. And we could also have bad times of different types, like the Great Depression or hyperinflation, where the cost (gold or hammers) of everything goes up.
Interest rate
Gold/faith/culture could have an interest rate, so they multiply over time if you don't spend it. And after you build a National Wonder called central bank, you could adjust the interest rate with some trade off. Otherwise, without an interest rate there will be an incentive to do min/max-ing. For instance, at turn 50 you need a worker, which you can buy for 200 gold. But you realize you could have bought him 10 turns earlier, when your gold first reach 200. So you lose 10 turns of worker's improvement for not buying it 10 turns earlier. So you decide to go back in time and load the game 10 turns earlier. But in real life, we don't spend all our money right away. We save because there is an interest rate. And we can make the cost of the worker vary with time and population size too.
