Awesome, the project is really cool, been trying it out for a few days. One thing I do wish, I wish the civs had more unique bonuses, instead of just recycling those from what they replaced. I’ll outline some ideas I have below because I love balancing stuff, but first, the Feitoria. Your version looks awesome, but it has one problem. The destruction animation still matches the original Feitoria, which you may want to fix. Now for my balance/change suggestions, don’t know what you think of this, but here are some ideas. Because I have so much stuff, I figured I might as well structure this more like an actual balance suggestion post, so I have arrows indicating what kind of change something is, as well as a 
for when I’m suggesting changing a civ bonus. Also, for all civs here, just remove Bombard Cannon, Hand Cannoneer, and Bombard Tower, because this is pre gunpowder:
Roman Empire:
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Blast Furnace added, they aren’t Byzantines any more, so this will be a good change. They are also meant to be a leading power, so it makes sense. -
Heavy Scorpion added, because the Romans were key users of the Ballista.
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Siege Onager added, because the Romans invented Onagers.
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Camel Line removed, it doesn’t really fit with the Roman Empire, because in my opinion at least, they should have a focus on Infantry, maybe Cavalry, and Auxiliary troops somewhat. -
Siege Engineers added, because the Romans were good Siege Engineers.
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Hussar Removed, to reflect a transition more from Auxiliary cav like the Republic, into Ranking officer cav like the Empire somewhat.
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Legionary is now a regional unit available in Castle Age, trained at the barracks. Stats wise, what you have now is fine.
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Praetorian infantry removed.
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Praetorian Cavalry is the unique unit solely, along with the Legionary, maybe increase the cost a bit, but increase the base damage by 1. -
Faster attacking fire ships removed, the Romans were literally scared of the sea, and most of their naval focus peaked during the Punic Wars, so the Republic should be better on water.
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Greek Fire removed, same reason as above.
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Logistica stage 2 added, a name is needed, but maybe lets Praetorian Cavalry turn into Praetorian Infantry when they die, but it increases their gold cost.
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The counter unit discount changes to Skirms, Spears, and Light Cav, and increases from 25% to 33%, making it reflect the use of enscripted troops.
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Free Town Watch removed.
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Masonry added, but the building HP bonus is halved at each level.
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Legionaries train 25% faster in Castle, and 50% faster in Imperial.
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Legionaries get +2 Pierce armor.
Roman Republic:
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Heavy Scorpion added, due to the use in the military, but I don’t think Siege Onager, because they aren’t the Empire yet.
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Siege Engineers added for the same reason.
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Legionary is a regional unit, like above.
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Praetorian Guard is now the unique unit, but cheaper than the mounted version, and with either -10 or -20 HP, with otherwise identical stats.
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Age up discount increased to 20%.
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Both Town Watch and Town Patrol are now free, reflecting how the early Roman Republic had to be ever vigilant against Barbarian attacks.
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Fishing ship discount removed, infantry now get +1 attack per age, starting in Feudal.
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The tech discount changes to making all techs research 50% faster, because early Rome was forced to adapt quickly to survive.
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Marian Reforms no longer enables Legionary training, but makes them cost 20% less instead.
Parthians:
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Thumb ring and Parthian tactics are free as a civ bonus, like the current Tatar one, giving them CA as a very viable strategy, it’s their famous style of fighting after all.
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War Elephants get a + 30% speed boost automatically.
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Mahouts removed, replaced with Horn Bow or Recurve Bow, making CA get + 1 range and fire 25% faster, further emphasizing that Parthian hit and run attack style. Alternatively, it could be removed frame delay and fire 33% faster, or +1 range no frame delay, all of them play into that historic effect.
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Cav Archers train 20%/30% faster in Castle/Imperial.
Greeks:
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Crop Rotation added, reflecting how some of the lands of Greece could be very hard and rocky.
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Architecture added, because the Greeks had some impressive ancient architecture, and it fits them.
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Siege Onager added, to fit with the Phalanx spear line playstyle, and also with like some of the Athenian and other intellectual war machines.
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Heavy Cav Archer and Parthian Tactics removed, because that was never a focus for the Greeks, they didn’t even use CA really.
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Athena War Academy replaced with Heavy Phalanx, giving spear line +1/+1 armor, and +1 range, or +3/+3 armor, or +3 attack, depending on personal preference.
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Greek Architecture replaced with Athena War Academy, making archers fire 25% faster, giving them a bit more than just infantry to play with.
Egyptians:
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Masonry and Architecture both added, I mean, the Pyramids. End of story.
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First two Cav armor upgrades added, the Egyptians used Chariots, so they don’t need the Meso missing stable.
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Light Cav, Knight, Bloodlines, Husbandry, and full camel line added. The knight has a chariot reskin I’m pretty sure, so it fits nicely, and the other things just fill in the stable a bit.
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Geometry replaced with Scythe Chariots, Knight Line deals +6 damage, and now deals trample damage.
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Military unit creation speed removed, and replaced with two bonuses, making all buildings cost - 20% stone, and stone miners work 10% faster. Maybe removed Guard tower, to reduce tower rushing. The Pyramids are again a bit motivation behind this, but also just their architecture in general.
Goths:
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Extra pop in Imp extended to + 25 instead of + 10.
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Architecture removed, it doesn’t fit at all with the Barbarian theme.
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The current hunter bonus replaced with Hunters work 25% faster, and huntables have + 10% food, because a lot of their power will really fall off in Imp.
Celts:
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Military units train 10% faster, kind of getting the Aztec bonus, but also letting them overwhelm more.
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Paladin removed, it doesn’t really fit now.
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Furor Celtica replaced with Druzhina, only it keeps the name. The whole tech is about being angry, and this fits the Barbarian theme better.
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Stronghold replaced with Tribal Remedies, letting infantry slowly heal naturally.
Those are just some ideas, if you want to use any of them for balancing purposes. I wasn’t too worried about crossover with actual civs, because you will only really use the ones above, and maybe Huns, which is why no crossover with them.