It will be interesting to see how they play out. In Endless Space and Legend, everything really pointed towards those minor factions integrating into an empire, forcefully or otherwise. Curious to see if there will be a way for some to survive until the modern age, as we have a few today.

Would be funny if you could release a city as part of the end of a war as an independent, and they would then be a city state/minor faction of of their own.

Yeah, having some minor faction that got the same role as principality in our world would be cool.

Also will minor factions change like empires do between eras?

For instance, Gaul turns into Portugal and switches focus from industry to trade, or the Mapuche turn into Argentina and switch focus from military to food.

Perhaps Minor Faction could be simmulated in a Civ-like way, with depending on the age and how much the minor civ likes you, you get a different bonus

For example, Let's look at the Vatican City- in the medieval age the Vatican gives Troops and leaders(simulating the crusades) while in later ages that bonus shifts to a scientific/cultural one(as to simulate the renaissance and the role rich patrons played to promote the arts)

I'm not sure how I feel about minor factions, permanently marking a faction for insignificance is a shame. Who is considred minor and major should be flexible. City states in Civ are so stale and predictable they feel lifeless heck the game forcibly ensures they never achieve anything as in the event they manage to take a city in war it's automatically razed to stop them building an empire.

my first thought was "barbarians"

maybe they'd also be like city-states?

It's not an easy decision I think.

I'm not a fan of independant roaming armies in civ-like games in general, and I never liked it in EL.

I like how each city state of Civ6 can grant bonuses that are potentially game-changing, or will bring some nice flavour. However I dislike how random it is - sometimes there's no city state in sight, or only "useless" ones for your playstyle...

I think I'd like a more dynamic system in Humankind.

Around every "main player" civ, you are guaranteed to have a bunch of minor civs that start totally bland. You get the choice to interact with them in 4 different ways.

Conquest (military) and assimilation (peaceful) will integrate their city inside your territory. Minor civs have their own armies that are significant in the early game but can't compete with major civs, especially on the long term.

Tribute (military) and allies (peaceful) will enable you to choose a bonus that this minor civ will grant you. They remain independant, but they provide a ressource, troops, and other kinds of bonus, depending on different factors such as the civ you're playing and the territory where this minor civ has spawned (they would only give naval bonus if they have access to the sea for example). Obviously that bonus has to be substancially better than what you would get by annexing them - if you choose troops, it could be for example that they give you experienced units, unique units, or a big number of cannon fodder.

As you progress through the game, your tributaries/allies will keep the same bonus, and with each era you get the option to assimilate them or to let them keep their autonomy (so you will annex them once their bonus becomes obsolete for instance). They can be conquered by other civs, and they can be made independant by peace treaties and diplomatic treaties. 

New bland civs will also be generated in each new era, every time on the fringes of major civilizations, and they can be specialized in different ways depending on the civ you pick for that era, but also the era they spawned in. But as you progress through eras, other major civs will be able to steal your minor civs more easily!

That way, everyone gets access to the minor civ types they want. I think it also makes sense to design them that way, because they are supposed to represent small territories that were on the way to get fully assimilated into bigger empires. They are not like fantasy factions that keep their own identity (mostly because they belong to different species). And they don't swing in allegance like in Civ6 depending on how many envoys you send. IMO this is also a great way to show how spheres of influence with "buffer zones", without making each war a war of conquest - instead there would be wars of dismantlement that would force warmongers to release all their tributaries, effectively reducing their military power til they regain control over them.

It also gives the opportunity to fight for something in each era, trying to guess where the new minor civs will appear, and competing to get their favours - or just stealing the minor civs that spawned between your empire and your neighbour.

I agree completely with Ezumiyr. I would much rather have dynamic minor states, than fairly one-dimensional Civ-like city states. 

I think besides the better gameplay one would get with a system of dynamic minor states, it would lend itself to the story aspect of the game more. Especially if absorbing a state with quite different culture can change yours over time or to the point of it reinforcing such things as regions in a state whether it be only a couple cities or a continent spanning empire. 

Yeah, that suggestion my Ezumiyr sounds solid. Maybe make it like a mix of minor states and goody huts. Being able to completely dictate their bonus might be a bit weird for me, maybe after either conquering or assimilating, you get to choose one among three choices, like the one we already saw in the Legacy bonus. Hm, the region on the map might need to be smaller than EL for these buffer states to work then.

I like the idea to support a minor faction which is not in my reach, to become a thread for others as well as the idea, that with enough support they even might become a civilisation themself.

I didn't read the messages above (my apologies), but even by the title - I support this idea. Indeed, relatively small Nations can be identified as separate small factions, and history has confirmed this. Again,

 I support this idea. And I think it will come true.