Still, since there is an existing scheme for alternate leaders build in, its worthwhile thinking about this, especially since the way it works with different city lists, colours and stuff will make it easier to implement your ideas into existing Civs. It will lead to some modders using it to just implement other leaders and some to split as they did before in Civ 5, Which means potentially less compatibility with different leader/civ mods. Easiest way to prevent that is to speak with each other and plan a bit ahead, but as you said its personal preference, so there probably wont be any consensus preventing a flood of different ways to tackle the issue. Civ 5 hasnt had this problem since there (originally) was just one leader for one civ.
For example, I wouldnt split Germany just in HRE and German Reich, since "inside" HRE alone has a vast amount of potential original Civs (Prussia, Austria, Saxony and so on). On the other hand, you could say this for many others as well (fe. Arabia). But then again, it would be a mess if everybody just splitted the heck out of every Civ and then throw their unique one civ/one leader mod out which conflicts with other approaches on civ-splitting (so in this case, Hirams Germanys/Arabia and mine couldnt really work together, if anyone would want to have both).
Maybe some Modders planning to do historical Civs should get together and make a plan beforehand which Civs should be separated. Then people could fill them with leaders as they whish, but there would be a bit of order at least. This way there could be a nice coherent and functional while huge leader/civ pack without mixing and messing up everything.
Well, but to answer the initial post a bit more clearly:
America -> would be fine to just add leaders; but you could also rename it USA and create other american Civs. OR you get cheeky and add Non-presidential (nonwhite/usa) leaders, like Sitting Bull or something, to the leaderlist of America. But I guess that wouldnt be a very sensible idea..
Arabia -> dynasty leaders would be fine i think, since Arabia represents early medieval, united Arabia. But like I said above, a huge area of nice Civs would be locked out. Playing other arabian nations along the original Arabia could feel a bit odd. But well, debatable.
Aztecs -> agreed (altough, how much is known about other historical Leaders of the Aztecs?)
Brazil-> agreed
China -> altough you could also replace it with warring states or 20th century warclans, it makes much more sense to leave china as a whole, yes. So many potential leaders!
Egypt -> I think keeping Cleopatra is fine, if youd add an ancient Leader and maybe also a modern time one it would feel natural. Although splitting Cleo to a Ptolemaic Civ would be great too, you could still use some other leader for that.
France -> same as China actually, too much great leaderstuff to go before you think of splitting.
Germany -> so, like I said above, I would be strongly in favour of splitting Germany further. On the other hand, its actually a different issue as with Arabia, when I just think again.. It still would feel natural to play as fe Prussia along with HRE ( and German Reich for that matter, too). Hm. Maybe it would be easier and still practical with just HRE and Reich, but my first concern was that it gets to limited for this diverse and complicated history in Germany. Ill have to think about that one more..
Greece -> same story as in Civ 5 actually.. Splitting would be nicer and more accurate (though messy). On the other hand, maybe you could do it like with Egypt, so drwaing a wider "greek" legacy and include early stuff like Mykene and later stuff like Byzantians, modernday Greece and so on. I dont know though, is it possible to alternate the Civs name with different leaders, too? Then this would make perfectly sense. Also, is it even possible to have a playthorugh with different leaders for the same Civ??
India -> yes, though the greek/egypt option would be doable too.
Japan -> agreed, altough also some similarities to the Greece problem. Maybe just differentiate between modern Japan and different older japanese Civs.
Kongo -> agreed, but as woth sumeria and aztecs limited info for good new leaders.. (maybe?)
Norway -> agreed
Rome -> agreed, but how to deal with east/west rome?
Russia -> agreed
Scythia -> dont know, really...
Spain -> yes, it would, but then the same is true for Russia! (Kiev, Moskow and stuff)
Sumeria -> Well, not too much info on them, but since Im not sure Im comfortable with semi-historical Gilgamesh, another leader would be good anyway. (ok lol, just looked at
wikipedia for other sumerians, and it appears there are tons and tons...)
You forgot England btw: with the old "England/GBR" discussion... But if youd add more early historical leaders, the obvious choice would be to leave it as England and create other biritsh Civs like Scotland instead.
I think the new way in which Civ 6 deals with different leaders gives definately different options than Civ 5 did. But a few questions remain till release to really be able to oversee the implications on modding, probably.
How you handle it probably comes down to the question how much you care about historical coherency, but the more coherent you try to make it it gets increasingly (over-)complicated and big. Modders of different understandings of these two dimensions will need to think about how to solve this, otherwise the mixing and mashing of different modders Civs wont work as in Civ 5.
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