Gotta say I love this game and I wish that I knew how to program so I could do some Modding. But I have a list of ideas I thought were pretty cool and that it might inspire some of you experts:
-Settlers carry religion. This was brought up in a post already, so it's been done, but I thought about it before and like the idea. Sorry for repeating. But when a settler is created in a city, it carries one of that cities religions with it.
-Settlers can become part of another city. A settler can be disbanded in a city to contribute to its population (increase by 1). We've all captured a city that was flipped back to the same culture or to another culture within proximity too early for anything to be done. This way, you can basically, bring settlers into the city and change the percentages in your favor.
-Buying promotions. For a fee, you can buy promotions for units. Each promotion would be more expensive than the last. It's realistic since every military goes through training, and some units go through more than others. I mean, every unit has a medic with them. That medic doesn't necessarily learn his trade on the battle field, he can get it before.
-War with Holy Cities. If the country that hosts your state religion is attacked, you automatically declare war on that civilization or your people get riot. This happens for both human players and AI. Naturally, No State Religion would mean that you would not go to war for this reason, but if you own a Holy City others will go to war for you.
-Bombers and Fighters never go obsolete. I really don't like the fact that these go by the wayside for stealth bombers and fighters. Even though most countries have the technology for stealth they choose not to build it because it's expensive and not cost effective for them. Therefore, I think that you could build either traditional planes or stealth. Stealth would be more expensive and have a high maintenance cost so that only a few would be built. As a tradeoff, they would not be able to be shot down except by other stealth aircraft (that includes SAM units).
-Revamp of the UN. Alright this is a big change, but I was thinking that the UN needs an overhaul to reflect the real world. This isn't meant to be political and I've seen a few threads get that way, so please try to keep politics out of it. Whoever builds the UN is an automatic member (for no charge, I'll get into this later) and can veto all war resolutions (I'll get into that as well). The builder would have the only veto. The UN should not have everyone in it, unless they choose to be in it. It should be free to join but cost like 30 gold per turn to be a member. Maybe have the cost be a function of size or total score, but not income. As a member, there is an automatic alliance with other members (though they do not change their perception of the other members, so there's no +1 "Member of the UN" or from Cautious to Pleased for being a member). The alliance would make members have a higher power ranking, and less likely of being attacked by nonmembers. It's an incentive to be a member. Anyone should be able to suggest resolutions in the general assembly including going to war on another civ. All civics should be passable. If a country declares war on another country, the UN can decide to intervene (by vote); or if another country proposes war, the UN can decide to help out. The lone veto can kill the resolution, the rest can vote yes or no. If the UN votes yes on going to war, a country can decide not to declare war and get a -2 "You went against a UN resolution." All the other countries would get a bonus like production for only units to help the war effort. If the UN votes no, a country can still declare war and get a -2 "You went against a UN resolution." Finally, if a resolution on a civic or trade is passed and a civ goes against it, they should be kicked out of the UN for 10 turns. At first I thought that getting kicked out is unrealistic, but I thought since there's no acceptance fee, only a yearly fee, there's no difference between not being able to propose or vote on a resolution and just being kicked out.
-The Space Ship cannot start to be built until Fission. On the harder levels this is the only thing that is shot for and it kinda kills the late game. It's really difficult to get a lot of use out of the cool new units. The Apollo Program and Space Elevator can be build before hand (though the space elevator should be called Mir, the International Space Station, or the Shuttle). After Fission, which seems to be the only true way to explore space, then production can begin on the space ship. This means that if you are going for this victory you will be going against the clock, especially against those who could win the total points victory.
-Settlers carry religion. This was brought up in a post already, so it's been done, but I thought about it before and like the idea. Sorry for repeating. But when a settler is created in a city, it carries one of that cities religions with it.
-Settlers can become part of another city. A settler can be disbanded in a city to contribute to its population (increase by 1). We've all captured a city that was flipped back to the same culture or to another culture within proximity too early for anything to be done. This way, you can basically, bring settlers into the city and change the percentages in your favor.
-Buying promotions. For a fee, you can buy promotions for units. Each promotion would be more expensive than the last. It's realistic since every military goes through training, and some units go through more than others. I mean, every unit has a medic with them. That medic doesn't necessarily learn his trade on the battle field, he can get it before.
-War with Holy Cities. If the country that hosts your state religion is attacked, you automatically declare war on that civilization or your people get riot. This happens for both human players and AI. Naturally, No State Religion would mean that you would not go to war for this reason, but if you own a Holy City others will go to war for you.
-Bombers and Fighters never go obsolete. I really don't like the fact that these go by the wayside for stealth bombers and fighters. Even though most countries have the technology for stealth they choose not to build it because it's expensive and not cost effective for them. Therefore, I think that you could build either traditional planes or stealth. Stealth would be more expensive and have a high maintenance cost so that only a few would be built. As a tradeoff, they would not be able to be shot down except by other stealth aircraft (that includes SAM units).
-Revamp of the UN. Alright this is a big change, but I was thinking that the UN needs an overhaul to reflect the real world. This isn't meant to be political and I've seen a few threads get that way, so please try to keep politics out of it. Whoever builds the UN is an automatic member (for no charge, I'll get into this later) and can veto all war resolutions (I'll get into that as well). The builder would have the only veto. The UN should not have everyone in it, unless they choose to be in it. It should be free to join but cost like 30 gold per turn to be a member. Maybe have the cost be a function of size or total score, but not income. As a member, there is an automatic alliance with other members (though they do not change their perception of the other members, so there's no +1 "Member of the UN" or from Cautious to Pleased for being a member). The alliance would make members have a higher power ranking, and less likely of being attacked by nonmembers. It's an incentive to be a member. Anyone should be able to suggest resolutions in the general assembly including going to war on another civ. All civics should be passable. If a country declares war on another country, the UN can decide to intervene (by vote); or if another country proposes war, the UN can decide to help out. The lone veto can kill the resolution, the rest can vote yes or no. If the UN votes yes on going to war, a country can decide not to declare war and get a -2 "You went against a UN resolution." All the other countries would get a bonus like production for only units to help the war effort. If the UN votes no, a country can still declare war and get a -2 "You went against a UN resolution." Finally, if a resolution on a civic or trade is passed and a civ goes against it, they should be kicked out of the UN for 10 turns. At first I thought that getting kicked out is unrealistic, but I thought since there's no acceptance fee, only a yearly fee, there's no difference between not being able to propose or vote on a resolution and just being kicked out.
-The Space Ship cannot start to be built until Fission. On the harder levels this is the only thing that is shot for and it kinda kills the late game. It's really difficult to get a lot of use out of the cool new units. The Apollo Program and Space Elevator can be build before hand (though the space elevator should be called Mir, the International Space Station, or the Shuttle). After Fission, which seems to be the only true way to explore space, then production can begin on the space ship. This means that if you are going for this victory you will be going against the clock, especially against those who could win the total points victory.