Great that recent updates and the new dlc has new techs/cards/scenarios that refer to a lot of important events in early modern history, like Peninsular Wars, Risorgimento, Great Northern War, Eighty Years War, etc. But the game still has not got any reference to the English Civil War, another important event with a lot of interesting military innovations.
Potential cards/techs:
Ironsides: the harquebusier’s look and its role as a ranged shock cavalry clearly refers to the ironsides. It could be a card or tech that ships harquebusiers and maybe give some more interesting bonus like the Koxinga.
New Model Army: maybe a card that reduces unit upgrade costs, as British rely heavily on age 2 units and need to spend a lot of resources upgrading them.
The Puritan Gentry (Oliver Cromwell): can be a unique politician with whatever bonus
Scenarios and historical maps
Battle of Marston Moor: one of the most important battles
Now the English Civil War itself only involves one in-game civ so it does not make a good historical map, but it could be combined with the French Fronde so that French and Spanish can also be included, reflecting an era of political turbulence.
Off topic: I see some very interesting Dutch technologies that refer to the sea beggars and Maurice of Nassau’s reforms (the real one, not the one that buffs halberdiers) in the Eighty Years War scenario. Do not know if they will cause balance issues but they could make some fun cards and techs.