Just a few things that the game is really lacking. Not just 'improvements' of what we already have, but totally new stuff. Suggestions open and welcome.
- Religion - A religion is founded in a civilization or city. It spreads across your empire and into other civs giving happiness, culture, diplomatic issues, etc.
- Corporations - Major corporations are built in cities. They spread their company across other cities to dominate wealth and control. Could also consume resources to create money.
- Regional technology development - Un-researched technologies owned by a neighboring civ will slowly leak into your research bank and possibly be granted to you.
- Immigration/Migration - Citizens from foreign civs can move to another civ's cities; citizens from one civ's larger cities will move into its own smaller cities.
- Colonies - Cities far away from capital and on other continents can be liberated to form colonies attached to its colonial "mother". Will provide mother civ with research, resources, etc.
- Health/Disease/Biological Warfare - Health and disease to slow city growth and/or prevent it; Damaging health as an act of war.
- Espionage - Using hidden spies to enter foreign cities and steal money, sabotage production, steal technology, etc.
- Foreign Influence and culture - Tiles and cities being taken and given to other civ by its influence in the land. Induced by one empire's large population or culture. Also, units (mainly workers) could be automatically transfered to civ with higher influence in an area.