I just wanted to throw my hat into the ring regarding Portugal, as I also find the slander pretty shocking
I think the search for a land UU for Portugal is fairly futile, what's incredible about Portuguese history is the period from the 15th to the 17th century in which this tiny, relatively poor country on the edge of the world created a global maritime empire through sheer audacity alone. Dom Manuel actually attempted to declare and enforce himself as the sovereign of the seas. *In the Indian Ocean*
If I were to redesign Portugal, I would focus on giving them a late Medieval / early Renaissance power spike focussed on trade and maritime warfare. I think the basic VP kit reflects that fairly well, but the 4UC kit loses sight of that somewhat. I would actually change the Nau to being a replacement for the frigate, available early. Naus were big, heavy ships with big guns designed to have the largest cargo capacities possible. They were not exploration vessels and were protected in the fleet by more nimble caravels. The Portuguese developed a square-rigged caravel-type ship called the caravela redonda / caravela de armada which would make a great UU for them. You could have the Caravela de Armada as an early unlocking relacement for the caravel to represent the innovative light ships the Portuguese developed that enabled their unprecedented exploration of the oceans. It would be a fantastic exploration ship that would make Portugal *the* Renaissance exploration civ, as in history, that could also be used to capture coastal cities, as the Portuguese did at Ormuz, Goa, Malacca, Zanzibar, and many other locations in that period. The Nau would lose its exploration role and become an early-unlocking heavy beast, providing long range support to the Caravela de Armada in attacking cities but also fulfilling its trade/economy-based role it has currently.
The University of Coimbra is just not that interesting for me, its just a medieval university. Instead, I would give Portugal the Casa da Índia as a unique replacement for the East India Company. Unlocking early, it would give bonuses to ship construction, great admiral generation, and some kind of bonus based on access to luxuries or luxuries sold.
With Caravela de Armada, Nau, Feitoria, and Casa da Índia, Portugal could lead the way in global exploration and trade and be a real naval powerhouse during the time period when it historically had such a freakish power spike. It's the interesting part of Portuguese history and the reason the civ is in the game, so I don't think it should be shied away from.
Completely unrelatedly, I'm sure it's been brought up before but I can't resist mentioning that the Celts never used scythed chariots, it's a common misconception. Celtic chariots were of an incredibly lightweight construction and designed for getting important high status warriors around the battlefield in speedy and impressive fashion. Scythed chariots did exist historically, but in the Persian and later Hellenistic world. The Celtic chariot was a very different beast.