At least for my two cents, I've come to decide that I don't like the idea of civ switching. I think it's better to have a set "character" you play as and fight against throughout the game, rather than switching throughout. It's more satisfying to finally kick Montezuma's teeth in if he's been a pest throughout the whole game than to defeat Santa Anna later on (EDIT: just in case, I know that Civ 7 has the same leader throughout, but I think it's retarded that you can have Napoleon lead the Mayans. This is aimed towards more reasonable civ switching ideas.) What I think I would do is to have a broader civilization, and then have smaller nations within it, somewhat similar to multiple leaders from Civ 6, which I think was a largely missed opportunity.
For instance, you could have a broader Anglo Civ, which as a bonus would give you gold upon conquering a city on another landmass than your capital (which would be able to somewhat represent British imperialism, American interventionism, and loosely represent the Anglo conquest of the island) and some sort of ship within the Rennaissance/Enlightenment/Industrial Age (depending on how fine the eras are, representing when the two extant Anglo states started to become the dominant naval powers). Then, within the civ would be the American and English nations, and possibly the Anglo-Danes under Canute (I feel like having both the Anglo-Saxons and the English could be redundant, since the one entirely became the other, even though it was through a massive culture shock from an invasion of a foreign culture. Canute would somewhat represent the Anglo-Saxons anyways, the Housecarls have a reputation as the Anglo-Saxon elite soldiers, even though they were a late addition from the Danes.) Each of these nations would then have their own bonuses, such as the aforementioned Housecarls for Canute.
Theoretically, this larger civ could be made even larger, and represent the northwest/north Germanics all together, as they all shared a large degree of cultural exchange at various points in history and all should be encouraged for overseas conquest, but I think that's too broad a brush. Assuming that you don't do that, similar to how Civ 6 allows one person to lead multiple civilization, you could have Canute and his Anlgo-Danes be under both the Anglo and the Scandinavian Civilization.