"Maintenance" or Corruption if you have been playing Civ since the 80's has always been my biggest problem with Civilization. Always going on distance to the capital (except with the old Communism tech) severely limits gameplay. I played TAM for Civ 3 A LOT...I just got Civ 4 for Christmas and looking for TAM was the first thing I did.
In 30 mins my corruption was so bad that my research rating could go no higher than 0% and I was bankrupt, and I only had 8 cities. I tried several different strategies, rushing for techs or wonders to unlock all the civics, but it did not work. These maps are HUGE. The reasonable distance for maintenance is the distance from Rome to the Alps...after that you are screwed. It is bad enough in normal Civ, but when you DOUBLE it from the beginning...there is no point in playing.
I know someone will probably try to use the "big empires fall apart" card, so I will use some defense. The Roman Empire, being the obvious answer, stretched from Mesopatamia to Britain. Even with the best roads and post riders in the ancient world, it took three months to get from one side to the other. And like every single civilization, there was some corruption. But that doesn't mean the edges of the Empire were any worse than the corruption in the Capitol. The most taxes came from Africa and Spain, not Rome. That is why the Vandal's rampage through Spain and conquest of Carthage was really the end of the Roman Empire in the west. (Unless you believe Gibbon, and Christianity made all those barbarians appear and destroy the Empire). But despite the corruption and destruction of the west, the eastern Byzantine Empire lasted almost to Columbus. Pretty durable for a big empire.
Another example being Genghis Khan, who conquered more lands and people in 25 years than the Romans could in 400. The Mongols could not make metal, cloth, or write, but JUST by creating a huge empire that connected Asia and Europe the Mongol Empire created paper currency, gunpowder, compass, and a thousand other inventions that made their way along to the Silk Road to Europe where they jumpstarted the Renaissance. The Mongols took European, Muslim, and Asian technologies and mixed them together, making something new in the process (like the cannon). It was an age of unprecedented trade, technology, and wealth until the black plague followed the caravans from Asia to every part of the Old world. If a quarter of Asia's population did not died from the plague, who knows where the world would be today. And despite the largest land empire of all time, despite the incredible distances rode on horseback across the empty steppe, the Mongol Empire was one of the longest lasting civilizations of all time. Although the Empire was split between Genghis' sons, and their sons, smaller Mongol dynasties lasted until around the mid twentieth century in Azbekistan.
Sorry for the rant. Someone tried to use the Macedonians as a reason for big empires falling apart, but that was because when Alexander was asked who should be his heir his answer was, "The strongest."
The size and the distance of the civilization should not decide the amount of corruption. It should be a set value because all civilizations, big AND small have corruption. It would stop what one person said, that the AI was building wealth in all their cities...I don't understand how you can play this scenario and not run wealth constantly.