How about from Civ 2? Anyone who has played the Fantastic Worlds expansion must remember the Jules Verne Scenario. I belive the object was to be the first to go from earth to the moon on their space cannon. The only problem was the only way to do that was sucessfully complete a number of quests (or trading for the reward technology) that involved defeating unique barbarian units usually with high defense but zero movement. Examples include defeating a "volcano" in Iceland that gave you the prerequisite tech to start researching "Journey to the center of the earth. Successful completion of quests usually gave a large monetary reward and\or a unique unit or wonder to build. Or the wandering unique barbarian Nautilus with a direct cash reward. I could list the quests if you want. A specific non-playable civilization also often was given special technologies that you would want to get by capturing their cities.
The only civilizations you are meant to play are the Anglo Alliance which consists of England, It's colonies, and the northern United States; and the continental alliance which consists of Napoleon's Empire (plus Russia) and the Southern United States. Also playable but at a disadvantage that makes winning the scenario extra hard are the Islamic League of North Africa through to Iran and the Mysterious East which consisted of China and Japan and finally the Secret Evil Organization which has only a few extremely well fortified cities around the globe with unique extra strong units to make sure they are a nuisance but not a threat to the two main playable civs. Not meant to be playable and at a huge disadvantage of development and tech are the Aborigines and the Exotics who were utility civs only there to make the quests work. The Exotics are probably not necessary since we have barbarians and their cities that do the same job but the Aborigines can still be usefull holders of the Punched Cards for the Time Machine quest.
The game lasted from 1800 to 1899 I think, and had just enough time to do all the quests and the require technologies to win, so think in terms of months. If anyone is willing to take this one up I will be pretty happy. I don't think it will be easy. I personally have no experience making scenarios or mods for that matter, but I can tell anyone who cares all about it.