1 Oil as a resource. Every army in every modern military campaign looks at their national oil reserves to tell how long they can carry out operations. Same with ammunition supplies. Moving units/fighting, etc would use up some points of the oil reserve. You'd need a lot to wage a major war.

There would be special oil resources that would appear on the map, which would provide lots of oil per turn. Lose access to them and your army can be in trouble (half movement or attack value or something), just like the Germans and japanese had problems in wwii. Oil would also be a major military objective (for modern armies)

Having to stock up ammo supplies would also give more primitive/less advanced players a better chance vs. the more advanced.

2. Supplies. Modern armies gotta get their juice and bombs somehow. Supply trains as a unit. One every 10 squares from a city, or 10 units or something to get them their food/ammo/fuel. This would allow people to cut off enemy armies, which has always been a big part of warfare (ie. Stalingrad)

3.3 types of city walls. Castle (high thin walls vulnerable to cannon but good vs ancient units), renaissance (low, broad, earthern reinforced fortifications good vs both), and fortress (maginot line like fortifications that have their own batteries).

4. Secret police. Can quell unrest in a city beyond the usual limitations of government (ie. in communist, only 3 can quell unrest. Secret police or interior ministry troops can quell more).

5. Elite Troops (US Marines, Republican Guards). Pay more but these guys are a little better in combat and cannot be bribed by diplomats.

6. Cabinet ministers you can assign to portfolios. They may help/hinder production/relations/culture depending on their various abilities. Only get to find out their stats by application (no stats available to player, must try them out to know).

7. Olympic games wonder. Create olympic team units to compete n win, for gaining international prestige and humbling your weak, unfit, flabby, enemies.

8. Build factories, mines, etc on the map and not just in the cities, forcing players to defend their territory more. To build tanks, build a tank factory. Can adjust economic/production priorities in cities so they can build more than 1 thing at a time. They just have to have the production to power everything.

9. Export/import of manufactured goods. First to create/discover automobiles means you are also the first who can sell them to foreigners.

10. Immigration/Emigration depending on the state of your civilization. Totalitarian regimes can seal their borders with secret police.

11. Mini/minor civs that can only have 1-3 cities or something. The map somehow often seems empty. More things to discover, find, unearth.

12. Ruins for destroyed cities (Amazing how clean the landscape is after you annihilate a people). Often there are interesting things to be found here. They may also generate tourist revenue if near one of your cities. They can be plundered of wealth once.

13. Occassional hurricanes that move across the ocean. Meteorological science can predict/plot their path. They emerge, move, weaken, and vanish, but if you're caught by them watch out. Two major invasions in history were thwarted by weather (Kamikaze Wind nailed the Chinese and the Spanish Armada got hit by a bad storm).

14. Instead of only being able to research one thing at a time, you can build labs to research different things.

15. The ability to sell arms/tanks/weapons to allies or just potential buyers, instead of having to provide units/troops. You could help by providing ammo or oil too.

16. Small techs. Not full fledged techs, like armour piercing shells or heavy armour or turbo charge engines, synthetic oil, improved rangefinders, sonar, improved weaponry, etc.

These would be sideline or subsidiary techs that might improve already existing units/equipment. Get armour piercing ammo and attack value of tanks/artillery goes up by one or something like that. Get radar and spotting range increases. Doesn't make the number of units go up, but provides a greater degree of variation between them.

I think some of these might be usuable ideas for civ iii. I really hope the game innovates more than civ ii did from civ i.

I'm sure I won't be disappointed after reading some of the ideas on these boards!

Phutnote Welcome to Apolyton!