stealth_nsk
Deity
I don't think the group which enjoys leading only their nation is that large. And Civ7 actually has a trick for them - if you pick a relevant leader, you could choose your civ in the exploration/modern age no matter which previous civs you choose. America even has two such leaders, white man and black woman, to cover most of the audience needs. So, I really doubt this audience would have any significant effect on the sales.I don't think you must be a history geek or even a civilization fanatic to build your immersion around leading a specific Civilization. There is a group of players who enjoy leading "their nation", especially among medium or light users. Just look how many social media posts are about adding "our" Civilization to the game. I don't have detailed data, but it is rather safe to say that forced swapping of Civilizations to a large extent is not welcomed in this segment.
Also, I dare to say history geeks will be more likely to accept this solution.
Actually, sales figures depend a lot on media representation. People watch youtubers they trust to make decision about whether to buy the game, and as I see so far, bloggers rate Civ7 quite high.
Selling DLC and expansions is a different story, which actually depends on player experience, so let's see how it goes.