I believe introducing more architecture sets is the solution to the problem of certain sets being shared by too many civs, and this will also make the game more beautiful. Ideally, I personally like each set to be shared by 2 or 3 civs as much as possible, 4 at most.
My current ideal list:
- Western Europe A: Britons, Celts
- Western Europe B: Franks, Burgundians
- Southern Europe A: Spanish, Portuguese
- Southern Europe B: Italians, Sicilians
- Southern Europe C: Byzantines, Bulgarians
- Northern Europe: Vikings, Goths
- Central Europe: Teutons, Bohemians
- Eastern Europe: Magyars, Poles, Lithuanians, Slavs
- Great Steppe (Nomadic): Huns, Cumans, Mongols
- East Asia A: Japanese, Koreans
- East Asia B: Chinese, Vietnamese
- Southeast Asia: Burmese, Khmer, Malay
- South Asia: Hindustanis, Gurjaras, Bengalis, Dravidians
- Central Asia: Persians, Tatars
- West Asia: Turks, Saracens, Berbers
- Africa: Malians, Ethiopians
- New World: Aztecs, Mayans, Incas
For some potential civilizations:
- If there will be Romans, they can join the Southern Europe B.
- If there will be Armenians and Georgians, we can introduce Caucasus set for them.
- If there will be Vlachs, the Eastern Europe can be split into
- Eastern Europe A: Magyars, Poles, Lithuanians
- Eastern Europe B: Slavs, Vlachs
- If there will be Khitans, Jurchens or Göktürks, the Great Steppe can be split into
- Western Steppe: Huns, Cumans
- Eastern Steppe: Mongols, Khitans, Jurchens, Göktürks
- If there will be Tibetans and Nuosu, we can introduce East Asia C set for them.
- If there will be Siamese or Chams, the Southeast Asia can be split into
- Southeast Asia A: Burmese, Khmer, Siamese
- Southeast Asia B: Malay, Chams
- If there will be Sogdians, they can join the Central Asia.
- If there will be Kanembu, Nubians, Somalis, Kongolese, Shona, the Africa can be split into
- West Africa: Malians, Kanembu
- East Africa: Ethiopians, Nubians, Somalis
- Bantu: Kongolese, Shona
- If there will be Muisca, Chimu, Tarascans, Mapuche, Polynesians, the New World can be split into
- Stone A: Aztecs, Mayans, Tarascans
- Stone B: Incas, Chimu
- Wooden: Muisca, Mapuche, Polynesians
NOTE: These are only assumptions and may not be realistic. For example, if there will be no Mapuche and Polynesians, then Muisca would most likely be with Incas and Chimu, even though stone buildings were not popular in Muisca. Also, the Vandals would be a difficult problem. Perhaps introduce North Africa set for Berbers and them. I don’t know.