So, here's my main idea and concept I think would be cool, and that is: all the leaders are new, and have never been used in previous civ games.
With this in mind, here is my lineup:
For the vanilla I would love to see a tribute to the first game, but also an expanded roster for a main installment, featuring 20 civs, with one leader for each.
1. Americans, Thomas Jefferson
2. English, Queen Anne
3. Egyptians, Sahure
4. Greeks, Cimon
5. Chinese, Kangxi Emperor
6. Romans, Constantine
7. French, Francis I
8. Indians, Jawaharlal Nehru
9. Babylonians, Nabu-apla-iddina
10. Aztecs, Itzcoatl
11. Russians, Elizabeth
12. Mongols, Töregene Khatun
13. Germans, Louise of Mecklenburg-Strelitz
14. Zulu, Mkabayi kaJama
15. Japanese, Tokugawa Yoshimune
16. Persians, Khosrow
17. Spanish, Ferdinand
18. Arabs, Al-Ma'mun
19. Inca, Mama Ocllo
20. Ethiopians, Amda Seyon I
First DLC expansion/season pass
1. Dutch, Frederick Henry
2. Turks, Selim I
3. Koreans, Jeongjo the Great
4. Maya, Lady Xoc
5. Iroquois, Red Jacket
6. Poles, Bolesław the Great
7. Portuguese, Pombal
8. Brazilians, Juscelino Kubitschek
9. Kongo, Nzinga a Nkuwu
10. Afghans, Ahmad Shah Durrani (NEW CIV)
11. Norwegians, Harald Fairhair
12. Khmer, Yasovarman I
13. Hausa, Amina (NEW CIV)
14. Phoenicians, Hiram
15. Bulgarians, Simeon the Great (NEW CIV)
16. Hawaiians, Ka'ahumanu (NEW CIV)
Alternate leaders:
1. Germans, Otto the Great
2. French, Anne de Beaujeu
Second DLC expansion/season pass
1. Gauls, Brennus (of the Senones)
2. Danes, Margaret
3. Berbers, Dihya (NEW CIV)
4. Ukrainians, Petro Konashevych-Sahaidachny (NEW CIV)
5. Malians, Mansa Sulayman
6. Nubians, Amanirenas
7. Puebloans, Popé (yeah, I know, but there is no reason not to try again, and find a way) (NEW CIV)
8. Canadians, William Lyon Mackenzie-King
9. Australians, Alfred Deakin
10. Muisca, Nompanim (NEW CIV)
11. Hungarians, Louis the Great
12. Assyrians, Naqi'a
13. Myanma, Anawrahta (NEW CIV)
14. Nabateans, Shaqilath (NEW CIV)
15. Venetians, Leonardo Loredan (and no, I don't want them to be a one city civ, they can have a city list, Venice is not just one city)
16. Indonesians, Kertanegara
Alternate leaders:
1. Russians, Ivan III
2. Persians, Artaxerxes III
Third DLC expansion/season pass
1. Swedes, Gustav Vasa
2. Austrians, Joseph II
3. Mapuche, Caupolicán
4. Māori, Hongi Hika
5. Georgians, David the Builder
6. Mississippians, Tuskaloosa (NEW CIV)
7. Haida, Cuneah (NEW CIV)
8. Vietnamese, Trưng Trắc
9. Ashanti, Osei Bonsu (NEW CIV)
10. Swahili, Al-Hassan ibn Sulaiman (NEW CIV)
11. Hittites, Puduḫepa
12. Tuscans, Matilda (NEW CIV)
Alternate leaders:
1. Koreans, Myeongseong
2. Romans, Julia Domna
3. Indians, Akbar the Great
4. Americans, Harry Truman
5. English, Henry VII
6. Myanma, Bayinnaung
Fourth DLC expansion/season pass
1. Lithuanians, Gediminas (NEW CIV)
2. Thai, Narai
3. Taíno, Anacaona (NEW CIV)
4. Malagasy, Radama I (NEW CIV)
5. Argentines, Eva Perón (NEW CIV)
6. Armenians, Tiridates III (NEW CIV)
7. Edo, Idia (NEW CIV)
8. Israelites, Salome Alexandra (NEW CIV)
9. Scots, Mary of Guise
10. Uzbeks, Muhammad Shaybani (NEW CIV)
11. Chukchi, Amulyat Khergyntov (NEW CIV)
12. Tongans, Tuʻi-tā-tui (NEW CIV)
Alternate leaders:
1. Greeks, Philip II
2. Berbers, Abd al-Mu'min
3. Spanish, Charles III
4. Zulu, Cetshwayo kaMpande
5. Egyptians, Thutmose III
6. Tuscans, Lorenzo the Magnificent