So.. Any advice on reducing maintenance and general unhappiness? Not a lot of luck so far.
Plenty. If your concern is the crippling unhappiness for adding a new city to your empire, there are a few ways to deal with it without any modding:
1> Raze the cities you conquer. If you want to capture them and keep them, then be prepared to deal with the consequences.
2> Don't go to war unless you have a bit of a buffer on Happiness. That is, if you're barely scraping by at +2, then don't start a war; wait until you've unlocked some Happiness-producing building and increased your net happiness to +10ish, to where you can afford the negatives of a newly acquired city.
This is how the AI already works. The AI players will prefer not to go to war until they're well above the 0-line, to where they'd have sufficient excess to handle the absorption of a few cities.
3> Play on a lower difficulty. Happiness is one of the main benefits of difficulties below Prince.
This is how the game stops people from going on Civ4-style rampages where they'll conquer half the world the moment they unlock a key military unit, like Tanks.
It's working as intended. Back in Civ4, once you got past the basic courthouse limitation of new cities, they'd be nearly as productive as your core cities, so anyone who conquered a neighbor in the early eras would gain an insurmountable lead over their foes. The whole point of this unhappiness mechanism in Civ5 is to prevent that situation from reoccurring; if you conquer someone, you're creating all sorts of problems for yourself that your more peaceful opponents won't deal with. Happiness is the most direct way in which you're penalized. Without this sort of mechanism, no one would ever win through a cultural or diplomatic victory.
But if you still insist on this course, then you can do quite a few things to make the game more conqueror-friendly:
1> Lower the per-city unhappiness from 3 (its current value) back down to 2 (the value it had when Civ5 was first released), or at least change the per-city value for newly conquered cities from 5 down to a lower value.
2> Lower the per-population unhappiness from 1.0 to some lower value. While you can't change the Defines value directly (since, as I noted before, it's an integer), you CAN alter the happiness multipliers in several other tables to achieve the same effect.
3> Add more low-tier buildings that add Happiness. For instance, change the Temple from +3 Culture to something like +1 Culture and +1 Happiness and make it no longer depend on the Monument. (I've done exactly this in my own mod, but that's actually to counteract an INCREASED per-population unhappiness that I use to slow down conquerors even more.)
Adding more +Happiness buildings makes it much easier to acquire enough of a buffer to afford the unhappiness costs of an extra city.
4> Change the rules for population of a captured city. Right now, capturing a size 8 city gives you a size 4 remnant, which can still add up to a good amount of unhappiness. But if you changed it to give only a size 1-2 city, you'll have less unhappiness to deal with.
5> Change the cost of a Courthouse, so the player can complete one quickly when they conquer a city.
You get the idea. There are a lot of things you can do if you want this sort of change. Just understand that, as always, the AI will not handle the changes well. The AIs might be much more aggressive than normal (since they'll be more likely to have enough happiness to trigger the "okay, let's grab another city" logic), or it might not change at all (in which case you, the player, will have a huge advantage). This is the most common problem with any significant modifications to the game's balance; so much of it is balanced around certain assumptions of game balance, and if you drastically change that, then things can break in all sorts of ways.
Even if the AI somehow doesn't choke on your changes, then it can still have unintended effects. For instance, part of the reason that the base per-city unhappiness was raised from 2 to 3 was to combat the "ICS" strategy; undoing that change just opens the door for that sort of thing all over again.
