Algonquian (Any) - 18
Anasazi / Navaho / Other SW NA - 18
Bohemians / Czechs / Great Moravia - 20
Nazca / Moche / Muisca / Other Andean - 15 + 1 = 16 : I'd love to see what the developers would do with the Muisca - they were a fairly complex, stratified society which had such an immense amount of wealth that they were the inspiration for the mythical city of El Dorado, and their language, history, and geography have decent documentation. Plus, I want to see at least one more South American civ in this series - Brazil and the Inca just aren't enough.
Olmecs / Mixe-Zoque / Other Mesoamerican - 9 - 3 = 6 : While it would be interesting to see the Olmecs included in this series (the Unique Civilization Ability and Unique Improvement shouldn't be hard enough to figure out and implement), their language hasn't been deciphered at all yet, and it doesn't look like it will be anytime soon. This means we can't find any leaders, nor any attributes for them. The Mixtecs would be a little less difficult, since they at least have some documented history and at least one known notable leader, but it would be somewhat difficult to find unique items for this civ.
Sabaeans / Himyarites / Yemen - 16
Tamil / Chola / Sri Lankans - 9
Ukrainians / Cossacks - 17