Oh fun, let me play as well:
(Bronze Era: Assyrians, Babylonians, Egyptians, Harrapans, Hittites, Mycenaeans, Nubians, Olmecs, Phoenicians, Zhou)
Classical Era: Carthage, Celts, Goguryeo (Korea 1), Greeks, Huns, Macedonia, Maurya, Maya, Persia, Rome
Feudal Era: Arabs, Aztecs, Byzantium, Franks, Inca, Khmer, Mali, Mongols, Saxons, Vikings
"Renaissance" Era: Dutch, English, France, Iroquois, Joseon (Korea 2), Ming, Portuguese, Russia, Spanish, Ottomans
Industrial Era: Cherokee, Ethiopia, Japan, Germany, Great Britain, Napoleonic Empire, Moghuls, Sweden, Thirteen Colonies, Zulu
Modern Era: Australia, India, Iran, Italy, PRC, Nazis, Turkey, USA, Soviets, Vietnam
The ones I am unsure about are in italic. For example, there kinda has to be colonial and modern United States, but you can't call them both the same...
What is visible, there will always be cultures that can go into two eras, and thus ones that are more to the end and others more to the beginning. So you will get weird coincidences. But then, not all civs will chose their era culture at the same time and some will stick. So the Spanish-Aztec encounter makes sense if one is renaissance (seriously, we need a better name, enlightenment? exploration?) and the other feudal. But I chose Saxons as the name for the medieval Germans since they can be English as well, but it makes it weird if they stay in the renaissance era. Maybe switch out the Portuguese there for Prussia?
The modern era stays strange, but this is the one where I hope it pays the most to stay in a civ from the previous era.
And they will probably leave a few spots for later additions regardless. For example, have Japan as Edo and Meiji, so you can't call them Japan here only.
