In my opinion the only thing to change completely in this game is the combat system. I dont think to be the only one that lost a unit when statistics gave me 99.7 % to win. I always appreciated the combat system used in the game Panzer general, where each units has his peculiarities as in Civ4, but each units has a value of 10. When it faced a battle it can have some casualities but never gone lost if not under particular conditions, for example surprised with an ambush. In this way you can have heavy casualities but you dont lose the whole unit only because a random number decides this turn you have to lose even when you have 75% or more to win. Even the chance to get a leader with some special qualities for a winning unit it would be nice in that game, I would like to see it on Civ4.