I have many ideas to be included in a second expansion. Before I begin 3 things should be noted: 1) I've never played a mod so many ideas could already be done better in something that exists. 2) These are not all my ideas, many are culled from other threads. 3) This is a second expansion, not Civilization V, so the ideas are (hopefully) relatively easy to implement.
1) Civilizations
i) My personal choices
Mesopatmia (Sumeria, Syria, Assyria, Babylon, Phoenecia, Hittites, etc... have far too much common territory to warrant
seperate civilizations. The Arabs are already an amalgamation and so would the Mesopatmians) UU is Slinger, upgraded archer with 25% bonus vs archer. UB is Ziggurat, upgraded temple that gives extra culture.
Khumer: UU is Viet Cong, infantry with woodsman 1 and 2.
Dutch: UU is Swiss Pikeman, stronger pikeman. UB is Dutch Bank.
Portuguese: UU is Cacador, rifleman with woodsman 1 and guerilla 1. UB is shipyard, upgraded harbour, that gives naval units experience.
Poland: UU is Winged Hussars, faster knights.
Hungary: UU is Magyars, stronger horse archers.
Austria: UU is Great Swordsman, stronger Men-At-Arms (see 4) Army)
Mayans: UU is Adzeman, axeman with woodsman 1 and 2. UB is Obsidian Workshop, a forge that has no pollution.
Ethiopia: UU is Ethiopian Rifleman (poor name. It should be whatever the soldiers were called that won at Adawa against the Italians).
ii) Others' choices that I liked, particularly when I noticed that my list is Europe-heavy,
Thailand, Iroquois, Toltecs, Ashanti, Songhai, and Congo.
iii) Civilizations that are not major enough powers to deserve to be included but probably will be anyway for scenarios.
Canada: (For the record I'm Canadian) UU is CEF = Canadian Expeditionary Force, stronger infantry (Canadian Infantry was feared in WW1 and 2). UB is RCMP barracks, upgraded jail that gives 2 happiness (In American West there were people then laws. In Canadian West there were laws then the people came).
Israel: UU is Merkava, stronger Modern Armour.
2) Navy
i) Make all sea and oceans squares improvable. Food (fishing boats), commerce (shipping lane), and hammer (whaling boats) improvements. Lower square base production or improvements harm other yields to balance. Land squares can have the canal improvement to allow ships to travel though land.
ii)Add Galleasse, Ship-of-the-Line, Dreadnaught, Missile Cruiser, and Nuclear Submarine. If civilizations are to be given multiple UUs then give many civilizations Naval UUs. Give England back its Man O' War from Civilization 3. German U boats, American aircraft carriers, Viking longboats, Roman Corvus Triremes, the naval equivalent of fast worker (Portugese or Dutch), Greek Fire for the Greeks, and even Korean turtle ships (out of Age of Emipires 2).
iii) Navy only promotions are a must and to be interesting should include gaining gold (plundering) through killing transports and % chance of capturing the vessel.
iv) Ships should be able to fight in port but give the defender the defensive culture bonus that land units get. Let naval units bombard cities to both damage culture defense and harm units. Resurrect an old improvement, coastal battery, to allow the city to damage the ship back.
v)Add naval leader traits: Explorer and Admiral. Explorer makes scouts, explorers, and ships +1 line of sight or movement; also trade route income increased. Admiral gives 4 experience to all naval units.
3) Airforce
Divide the current bombers into 2 seperate units: Strategic and Tactical Bombers. Strategic Bombmers can pillage, kill population in cities, try to destroy existing buildings, and destroy hammers for a unit being built in a city. Tactical Bombers can dogfight better than Strategic and can pillage, damage land units, including a chance to strike first at anti-air land units. Fighters get an additional ability to escort. When a friendly plane on a bombing run is about to be attacked by an enemy fighter a friendly fighter on escort fights with the attacker first. This uses the fighter's movement so it can not intercept the same turn. All planes should be allowed on carriers.
4) Army
Add Men-At-Arms, Self Propelled Artillery, Attack Helicopters, and Cruise Missiles. Have a paratrooper promotion. Have cannon appear much earlier in the tech tree. Historically cannon were adopted into the military before hand guns. There's something about musketeers grouped with catapults that makes the history buff in me cringe.
5) Wonders
Louvre, Area 51, Circus Maximus, CERN, Easter Island Heads, Maginot Line, Space Station, Sphinx, and Krak des Chevaliers.
6) Civil War and Resurrecting Civilizations
First free up the civilization from its colour. So Japan could be yellow and France gray. Also give each civilization at least 2 leaders. Allow multiple players to be the same civilization, just not the same leader. Single player games couldn't start with 2 of the same civilization. Do away with the 18 civilization cap.
I'm a peaceful player. I've never played to conquer the world until I run out of things to build around the rifleman era. Most threads indicate that the war game is essentially over by the industrial era. To keep large empires (most likely the player's) from winning that early I suggest reintroducing civil wars. Large empires also cause unhappiness with the citizenry (wasteful central government). If too many cities have at least one unhappy citizen then some of those cities succeed and form their own nation, which is the same civilization as the former owner with a different leader.
That would lead to city razing as a way to get around your empire having a civil war. To that I propose resurrecting civilizations that were wiped out (or introducing new ones) at a later date in territory that has no owner. Giving them several settlers, workers, and soldiers should give them a chance of rebuilding. This is like what happened in Alpha Centauri.
7) Spies and Diplomacy
i) Allow alliances, open borders, and defensive pacts from the start of the game.
ii) Allow spies to be built much earlier. Give them the ability to bribe units and nuke cities.
8) New Eras
Go into the future with the Information and Nano eras. This will require disabling the space victory and turning the Apollo Program and Space Race into wonders. A Science Victory would be created similar to that in Alpha Centauri. It would be a huge wonder at the end of the new tech tree.
Currently, the game has melee infantry is obselete and upgrades into ranged infantry, and cavalry upgrades into helicopters. If current trends prevail, the battleship will become obsolete as air power dominates more naval conflict. In the future, my guess is, tanks will become obsolete for mechs.
i) Units
mechanized infantry -> laser infantry -> augmented infantry -> robotic infantry
marine -> commando -> genetic warrior aks genies (name from Buck Rogers) -> hybrid soldiers
artillery -> self propelled artillery -> missile battery -> fusion battery
modern armour -> grav tank
modern armour -> mech suit -> goliath
sam soldier -> F.O.E. battery -> ion battery
gunship -> attack helicopter -> hover plane -> repulsor ship
attack helicopter -> airbase (airborne version of an aircraft carrier)
jet fighter -> plasma fighter -> orbital fighter
stealth bomber -> solar bomber -> orbital bomber
submarine -> nuclear submarine -> Leviathan -> Poisidon
destroyer -> tempest -> avatar
transport -> cryogenic transport
ii) World Wonders, those taken from popular science fiction and Alpha Centauri
Martial Colony, Cloning Vats, Fusion Reactor, Biosphere, Clinical Immortality, Magma Tap, 0-point Reactor, Dinosaur Park, World Archives, Cryrogenic Repository, Controlled Evolution
World Wonders, aritist based, so not from popular science fiction, completely made up
Celestial Palace, Selkirk Memorial, Hermaz's Fractals, Artificial Borealis, Saints' Gallery
iii) City Improvements
Cloning Facility (instant population 10, cheap), Airbase, Commercial Teleporters, Weather Control, Life Recycler, Archology, Mass Transit, Digital Library, Genetic Sculpter, Automated Sentry System, Nano Assembler, Treatment Plant, Theme Park, Commercial Hub, Orbital Launchpoint, Orbital Hydroponics, Orbital Solar Arrays, Asteroid Mining Facility, Solar Power Plant
iv) Technology
Use most of Alpha Centauri's tech tree. A few techs to link the existing tree and Alpha's:
Space Habitation, Virtual Reality, Hydrogen Fuel, Quantum Computers, Solar Power
9) Religion Ideologies
i) Give each religion different benefits. Yes, I realize this is a politically correct landmine. I just don't like each religion being exactly the same.
ii) Religion becomes a moot point in the late game. With the advent of Free Religion every computer and most human players
will switch to it. I like the idea of reusing the religious system in the form of Ideologies. Ideologies function like religion, each civilization has an official one and it spreads to different cities like religions. A new unit, Philosophers, spread it like Missionaries. Civilizations of different ideologies hate each other while those of the same like each other.
The ideologies are
Harmony +health, +forest and jungle yields, founded with Environmentalism
Dominance +unit exp, founded with Fascism
Order +happiness, founded with Communism
Freedom +culture, founded with Liberalism
Wealth +money, founded with Corporation
Knowledge +science, founded with Scientific Knowledge
Nihilism +production, founded with Fission
This does have the disadvantage that there is a lot of overlap with existing civics.
10) Miscellaneous
i) Have region (eg: Middle East, Asian, Classical, ect...) specific look to buildings and improvements. Group civilizations
by region at the start of the game.
ii) Bring back colonies.
iii) Being able to plant forests.