My idea for SMAC2 is somewhat in opposition to Diplomats, which while I agree offers a rich storyline, does not reach the full potential for SMAC2 as a build/discover game.
My idea (basic storyline), as civilization on Earth slowly collapses due to overpopulation and overstretched resources an extra-terrestrial colonization drive is started. Many worlds potentially suitable for human habitation have been discovered and spaceships (or Star Arks, if you will) are constructed by whatever organizations have the resources and technology. Thus, there is no organized UN style single colony ship, rather hundreds of colony ships heading to dozens of worlds. The factions could be highly varied, some faction ideas include:
Colony ships sent by Countries, to continue the nationality on the other planets. (So, there could, for example, by an Australian faction)
Colony ships sent by multi-national companies, for varied reasons.
Colony ships sponsored and led by ultra-rich individuals. Motives and objectives could be highly varied, among this class could be several “social experiments” (ie the Human Hive).
UN Sponsored colony ships, to act as peacekeepers/humanitarians/law makers on the new worlds.
Cults (rich, influential ones, obviously).
Aliens…
And more….
And a fully featured faction editor, with built in rating and balancing (If you have played MOO2 or Stars! Before, you will know basically it would need to be like…)
Depending on the game settings, a number of colony ships (say, 1 to 16) land on a world, with various placements, for example you could set up a teams game where teamed factions land close together.
A more advanced world builder and climate model would be used to make more detailed worlds with a far greater depth of features and terraforming choices, the worlds should be able to range from:
Completely airless worlds (like Mercury, or the Moon).
Cold, dry completely barren worlds, which must be completely terraformed from the ground up (like Mars)
Barren frozen planets with ice oceans.
Barren desert worlds with little water.
Worlds with little life, but at least some biosphere.
Worlds with a fully developed biosphere, but somewhat incompatible with Humans (like Chiron)
Paradise worlds requiring virtually no terraforming (like Earth)
These worlds would be fully modeled using the climate engine, the actions of the factions could change many variables, such as atmosphere density/makeup, wind, rainfall, rivers, oceans, volcanoes, ecological disruption…
Each world would also have a unique combination of properties and challenges.
The sorts of things which the new colonies could be blessed or cursed with (other than each other) could include:
Extremely dangerous wildlife
Existing civilizations of varying degrees of evolution.
Ancient civilizations which awaken as their world is terraformed back towards livable conditions.
Extreme seismic or meteorological activity.
Unusually abundant sources of energy (i.e. Uranium deposits)
Highly fertile oceans.
And many more…
…
These global properties would determine the types of land marks which appear, possibly open new tech branches, and largely determine which way the game unfolds (including book of planet). Games could be set up so just surviving the natural hazards would be an achievement in itself (hence the ability to have just 1 faction
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And it could go the other way, a world where the only challenge is the other player, with nothing left to random events.
Ideally, it would be possible to have SMAC as a subset of the game, so AC could be played as a game mode (7 Chiron Factions, random starting positions, Chiron type world settings, dangerous wild life, plant growths incompatible with earthly life). But also it should be possible to play a completely different type of game (for example, gaining supremacy of a volcanic world which is frequently blasted by meteorites and food can only be grown in self-contained farming units, or on a Mars like world which results in a slow game start, and requires a lot of work to make a strong faction, and global co-operating to fully terraform)
Admittedly, the game would be somewhat more ambitious and larger in scope than SMAX, and probably worthy of it’s own title, rather than just SMAC 2. But I think genres should evolve and sometimes take great leaps forward.
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Great ideas man 
