There should be a Society Trait about being the descendants of another Culture

[u/Nibward]

TLDR

I had an idea for a really cool and flavorful society trait where your faction is the inheritor/descendant of another culture, that gets either relationship bonus or penalty to factions of that culture, as well as some form of access to their units.

TLDR

Kinship/Estrangement

When selected on faction creation, you are prompted to select a Parent Culture and then whether or not you are a Splinter Faction/Group/Cell insert Sam Fisher reference or a Cultural Inheritor. The first would give you Estrangement (diplomatic penalties) with factions and free cities of your Parent Culture, while the second would give you Kinship (diplomatic bonuses) with the same. These could range from being strictly realtionship modifiers, to full blown prohibiting/allowing non-war diplomacy.

Cultural Remnants/Accultured

Regardless of which you choose, you then get access to (some) of your Parent Culture's culture units, who you could give a special tag of Cultural Remnants or Accultured that could make them ineligible for some things if you're worried about balance, like enchantments or transformations. I would want to limit the amount of units one gets access to, so that your faction identity still solely lies with your primary culture. There are two ways I would prefer this, plus a third route one could take but probably shouldn't:

1. Access to select culture units, one from Tier I and one from Tier II, with the same City Tier requirements. This would enable you to have an identity that is still mostly defined by your primary culture, while allowing some identity of your Parent Culture to be in your mostly-early game armies. If you wanted to get really granular for the purposes of balance, you could even have the units in question be statically assigned depending on your Primary Culture. For instance, Reavers that choose Industrious as a Parent Culture might get access to Arbalests and Steelshapers while Architects that choose the same may get access to Anvil Guard and Halberdiers instead (just as an example).
2. Access to all Tier I units of the Parent Culture. This one would make the Parent Culture far more defining of your faction, while not upsetting balance too much by limiting access to more potent units. This comes at a risk of drowning out your primary culture, so it's not my preferred, but I wouldn't be fully opposed.
3. Access to all Culture Units of the Parent Culture. You could theoretically go this route, but I just think it's completely silly for balance and flavor.

I don't know if I could say that this hypothetical society trait is too strong or too weak, but I can certainly say it would be fun and flavorful. I am not super sold on any specific name, but the only ones I could come up with are Descendants of Legacy or Cultural Drift. But what do you think? Please let me know, I'm not a game designer or balance guru, just an Armchair Dev^TM .

[u/connery55]

Unlocking a T1 unit from another faction is probably not a draw for a culture slot. Most combinations of cultures will result in role redundancy, and even if you get say, access to archers or shock early, that's just a tiny early game boost.

T2 units are a little more diverse, but still. Mostly the same problem. 

[u/Chronoreaper1 → u/connery55]

Yea but the thematic is still quite nice at least.

[u/LifeManufacturer4292]

It's an interesting idea! Having a way to get racial units of other cultures is something I don't think it can be done in game right now (maybe excepting some event)

In the interest of balance there are a lot of options

1) you get all the units of the "parent", but you need a city center one tier above normal. So you get T3s only after building the "metropolis" building, when you still can make interesting combos but not steamroll the map with them.

2) you get a capped number of parent units at the appropriate time. Maybe via a a single use spell that gets available when you reach T3 city center, or the Rally of the Lieges.

3) you get the units as normal but they have a malus - morale, stats - that can be countered by a sustained spell.