It's easy enough to come with a worthy leader for every Staple Civ who hasn't been repped in the franchise yet. Some examples from the top of my head:
Americans: Thomas Jefferson
Arabia: Arwa al Sulyahi
Austria: Franz Joseph
Aztecs: Axayacatl
China: Gaozu, Yongle
Egypt: Thutmose III
England: Aethelflaed, Walpole
France: Cardinal Richelieu, Henri IV, Philippe II
Germany: Otto III, Empress Matilda, Konrad Adenauer
Greece: Alcibiades, Leonidas, Solon, Themosticles
Haudenosaunee: the Brants, Jigonsahsee
Inca: Topa Inca Yupanqui
India: Nur Jahan, Rajendra Chola
Japan: Hojo Masako, Meiji
Mongols: Mandukhai, Ogodei, Tamerlane
Netherlands: Johan de Witt, Michiel de Ruyter
Ottomans: Roxelana
Persia: Abbas, Khosrow, Mithridates
Poland: Boleslaw I, Jan Sobienski III
Phoenicia: Hanno the Great, Hamilcar Barca, Hasdrubal Barca, Hiram of Tyre
Rome: Livia, Gaius Marius, Marcus Aurelius
Russia: Aleksandr Nevski, Olga of Kyiv
Spain: Pelagius
Vikings: Cnut, Margarethe
Zulu: Chestwayo
I would advocate a Civ 7 with a completely new set of never-before-seen leaders.
(but especially without Gandhi and Alex)