New civs such the Incans, Mayans, Dutch and Portugese to name a few, and some must be from the African region in addition to the Zulu. New Traits would be great as well, these could include Agricultural(Focusing on food and Growth), Political(Concentrating on better governments and 1 turn Anarchy), Artistic(Mainly Cultural), and Barbaric(No War Weariness to starting Wars, among other things). Better Diplomacy like everyone has said would be good too.
Also, they should try to make Religion a concept that is significant to gameplay that will vary between race, for example the Greeks, Egyptians, and the Aztecs would be Mainly Polytheistic, while the Americans, and Britains would be almost all Monotheistic. What each religion affects would be decided by someone else.
I also like the concept of assigning production points to Resources and The "Firepower" Idea and giving ranged units limited Zones off control.
Of course these are my opinions