Rework Unhappiness Penalty
I notice a lot of post about happiness are on how it should be easier to get but honestly I think earning happiness works fine. After my first 2 games I've never really had a problem with happiness since I learn to properly manage it.
The raze cities option rarely comes up as I only raze a city if it's in a crappy position and not worth maintaining. I don't raze because I don't have the happiness to support them. In fact I rarely even Puppet cities anymore.
I think the problem is no so much in "GETTING" happiness as it is in the "PENALTY" for having too much unhappiness. I think a better approach is to rework how the penalty system works when you go unhappy rather then simply making it easier to stay positive.
The reason for this is because frankly it's pretty stupid that when you get -10 unhappiness regardless of empire size you suddenly take this major penalty to EVERYTHING. The worst of which is the hit to your military forces which in the middle of a war can cause you to loss everything, I mean come on -50% ?!? you might as well have them drop 1-2 tech levels. And if your already fighting someone who's a tech level higher then you then your screwed.
----------- New Unhappiness System ------------
So here is what I think the unhappiness system should be like.
1) Bring back Rebels in cities when you go into unhappiness
2) Rebels appear in Occupied cities first, then puppets, then your main cities.
3) Rebels appear in cities farthest from your capital first as well after #2.
4) Rebels appear in a city until it reach 50% of the Population being Rebels which causes the city to be in open revolt. No production, gold, science, and etc.
5) Cities in open revolt loss 1 HP per turn. If they reach 0 HP they will leave the empire returning to the original owner. In case where you are the original owner they will join the nearest AI Empire.
6) If you Garrison a unit in the city that is in Revolt and has 0HP the city will do damage to the Garrison unit as if it had done a normal attack. Once the Garrison unit is dead the city will leave your empire as mentioned in #5
7) Newly Rebelled cities will spawn a unit to help defend them following the same rules that Military City States spawn units.
------- Example --------
As for an example of how this would work say you have -20 Unhappiness and 2 Occupied/Annexed cities (10, 8) pop with 1 Puppet city (12) pop and several normal cities (15, 13, 9, 6).
First it would see which of the Annexed cities was farthest, lets say it was the 8 pop, so it would turn 4 of the pop into Rebels and the city would then be in revolt. Next it would look for another occupied city, this time the 10 pop, and place 5 Rebels. So we are up to 9 of 20 with 11 to go.
Then it would move on to Puppet city of 12 pop and place 6 Rebels in there. Then having no other Annexed or Puppet cities it would move to your normal cities. Say 6 pop one is the farthest from the capital. So it puts 3 Rebels in that city pushing us up to 18 of 20 unhappiness accounted for, only 2 remain. Lastly say the 13 pop is the next furthest city so it gets 2 Rebels in it which only lowers it's production by the loss of those 2 citizens who aren't producing but is not yet in open revolt.
As you can see the core of the empire remains productive while the outer reaches of the empire become hard to hold on to and maintain. In this example unless the player does something to resolve this he's likely to loss the cities he recently conquered to open revolt. This also has the effect of feeling like your trying to win over the people a bit more who are unhappy you conquered them.
------- Conclusion --------
I think this system does a much better and more realistic job of undermining large empires. After all the biggest problem with having a large empire was always holding it together as a lot of people thought they could do a better job of managing it and would want their freedom.
Since the main goal of unhappiness seems to be to curb rapid expanding military conquest I think this approach does a much better job of that then the current penalty system. Since there is the chance cities will return to their original owners there is a lot more pressure on keep them happy. This was one of the key elements in previous Civs as a city that had a lot of unhappiness would rebel and join another Empire. Meaning your really didn't want them to rebel more so then simply going, oh well I don't get any production from them.