Civ isn't designed to have a lot of empire management and I'm okay with that. Although... it would be nice if it had just a little more.
In particular. I'd would be great if maintenance costs ratcheted up more over time (Sea Walls sort of do that - but not well) and power should be more of a requirement - it's just so optional.
This is part of what I think is a wider problem: Costs of all kinds rising over time, but being balanced (at least sort of) against rising income. - And not just for 'Gold' costs: one big disconnect in the game now is how the rising Production costs of units are not matched by rising Production capacity even with fully powered Factories in the late game. To use a simple Historical Example, it took the Romans months to manufacture enough weapons and armor to equip a Legion, and a Legion was not considered fully trained and reliable until it had been in existence for at least 5 years. In WWII, the USA could manufacture enough tanks, vehicles and weapons to equip an armored division in about a week, and have the division fully trained and operational in 1 year.
Oh, and the armored division had about 3 times the number of men that a Legion had, and required about 40,000 tons of steel/oil/rubber for its equipment and vehicles where the Legion required about 120 tons of iron for its weapons and armor.
The difference is in Orders of Magnitude, but the Production capability increase from the Industrial Revolution more than matched it.
I'd like to see the Industrial Revolution/Industrial Era start a massive increase in both Gold and Production income, and Gold and Production costs. A sailing ship's maintenance amounted to replacing sailors who drowned or retired, torn sails and rotten rope and occasional rotten plank - and they lasted a long time: rthe wooden sailing ship-of-the-line
HMS Victory was in active service for almost 60 years, far longer than any modern (iron/steel) capital ship. A steaming Ironclad required constant fuel (coal) and mechanical maintenance in skilled mechanics, spare parts, machinery. The constant Maintenance Costs, basically, went through the roof compared to earlier ships - unless you had a heavy industry infrastructure in Steel Mills, Shipyards, coal and iron industry (Factories, Powerplants) to produce what you needed in quantity.
Put simply, a Pre-Industrial Civ cannot easily build, and cannot possibly afford to keep, an Ironclad or later warship.
To use an In-Game Example, the battleship
Minas Geraes, Brazil's UU, was built for Brazil by Great Britain, and had to be upgraded in the Philadelphia Naval Yard because Brazil did not have the industrial infrastructure to either build or maintain a battleship: Minas Geras' sister ship rusted away at dock because they couldn't even afford routine running maintenance on her, and that disconnect between Requirements and Capabilities should be in the game.
BUT balanced carefully, or we'll get the same disconnect we've already got in cost of units versus Production now.