After several years away, I’ve been playing 1.16 a few months now (probably too much), and I have a few possible suggestions. But one thing especially comes to mind (my apologies if this has been brought up before).
I feel like the Greek and Roman civilizations by nature operate quite ahistorical. I’m sure a number of things can be done, and I don’t know if this is a priority. However, the biggest issue with the Romans is that their state date is too early. 753 BC was a mythical founding date, and even if accurate, Rome started out as a small village and subject to Etruscan rule. It is definitely ahistorical for the Romans to show up in Italy in 753 BC with two legions and fleet, which leads to the player embarking on a Roman conquest of the Mediterranean in a time when Rome was a tiny village. For much the same reason the Dutch starting date was moved to the 1580s, I think the Roman start date should be later. I would suggest c. 509 BC, when the Roman Republic was created. That would be a more accurate time for Rome to emerge on the scene and begin conquests.
Of course, the problem with this is that it’s already a major crunch accomplishing Rome’s UHV. Perhaps the UHV could be changed, but I have another idea that could contribute to this (and the idea I really wanted to bring up).
It occurred to me that there are too few cities in the ancient period. And that makes sense: settlers take time to build. However, if you think about it, many of the cities built by Alexander the Great, the Romans, and the Arabs were founded by decommissioned soldiers. Alexander seeded his empire with Macedonian military colonists, founding the many Alexandrias. The Romans, after the chaotic political upheavals around the land reform attempts of the Gracchi, mostly gave lands to decommissioned veterans, who were settled as colonists in the provinces, especially in strategically useful sites (rebuilding Carthage and Corinth, and founding important cities like Trier, Cologne, and London). Likewise, the Arabs planted military colonists in garrison cities (amsar), founding Cairo, Mosul, Kufa, and Kairouan, among others, this way.
My question is, would it be possible, both within the game engine and within your vision for the mod, to allow for military units to found cities? Perhaps when running the conquest civic, since the planting of veteran colonies is a strategy used by expanding empires to quickly assert control over conquered territories? This would potentially speed up the Roman UHV, since the Roman player can concentrate on military production (with the help of the Coliseum), and use those soldiers both for conquest and quickly settling cities (like the Roman really did). It would also help represent expansion of other great pre-modern empires.