Since most units are only usable for a short time it should not be hard to spread out the new units in different ages to solve that problem. And there could be more unique hex improvements. For instance: Babylon could have a ziggurat as a better temple. Sweden could have a better forest improvement called Mill town that give an extra production and gold and/or a light field cannon as uu. Denmark could have longboats instead of triremes that can travel on ocean square from start England could have a better battleship and/or a new sort of way to create colonies or protectorates of city states. Germany could have their fighter Messersmiths (or how it is spelled). France can have Mote and bailey (or how it is spelled) the scenarios improved fort Rome can have a better aqueduct and/or perhaps a improved courthouse called Forum giving extra happiness and making conquering worth wile. China could have a cheaper infantry and/or improved factory perhaps more production but cost one more unrest. . The list goes on. Its not hard to think of new things for each civ that indeed would make the game more fun. I would also like new buildings that buff certain resources. For instance a textile mill that give an extra gold and culture on cotton and silk and sheep.