Migration and populations moving is obvious. I was moreso saying that we wouldn't see "ethnicity" like another user mentioned wanting.
A possible Immigration mechanic would be one of the main uses for heritage/religion/profession since there should be some motivation for population to immigrate in first place.
God knows how it'd fair if a population that is identified in some way as "Chinese" moved to a Japanese city to become "Japanese" lol.
Immigrate do not mean to change their identity. Did Jews lost their religion or heritage after many centuries around the world? And even if some peoples did what is the problem about chinese immigrrant integrating to Japan? If we change this to Irish moving to USA and become Americans, should we "LOL" about it?
Either by conquest, immigration or alliance peoples of different cultures endend living in new lands and leaving his mark. In game this could be name Tradition, as a cultural legacy that do not even need to be blood-related since many of these include things like beliefs, art styles, techniques, foods, etc.
Also, it'd be too annoyingly complex IMO. I'd rather see more complex trade relations and city dynamics (Something the player can control) over complex population migrations/ethnic groups (Something the player can't control). I can just see this getting out of hand really fast.
It would be as complex as developers want. All game mechanics could be complex, included warfare, religion, economy, etc. But all of the ones on game are already abstracted and simplified. The actions of the players would have obvious effects like:
- Embrace Freedom of Religion then more religious minority population would move to your empire from the other regions where they live oppresed.
- Build more Universities and more Academic population would immigrate to your nation.
- Be fair with your population of X heritage and their homeland country would have a nice diplomatic bonus.
There is nothing realy complex about it, is a system of pros and cons from player actions based on the affinity to X or Y identity parameters of population units. It is in player control because population would neither immigrate or change heritage if there is not a significative action from the players.
Population "identity" would work well in an industrialized world...but in my opinion I think it should not be implemented. Attaching an identity to a population unit that could be transferred between civs would be a disaster of controversy (I'm sure Georgian populations would love joining Russia...) and this level of hyper-realism just isn't needed.
In game Georgia can turn muslim, while Russia can nuke and raze georgian cities and this is OK, but would be wrong to have georgian pops moving to Russia?!
If on game gerogian population have a good reason to move to Russia they would do, you know players could actualy play Russia as a more frienly nation if they want.
An idea for this I had was to make culture of increasing importance throughout the eras-civs with lower cultural output may have a harder time keeping citizens loyal and as a result, these citizens may join other civs with higher culture. It makes culture as a currency more valuable and forces even the hard science-focussed civs into acknowledging and growing this vital metric.
Similar to CIV4, where strong NAMED cultures can flip the loyalty from one civ to other. By the way in your model georgian population would still end joining Russia if the later have higher culture.
Population migration due to natural disasters, famines, or wars is something that could happen between civs-just don't attach that identity to them since they will just ruin things (And add too much unneeded complexity)
Culture should definitely still be tied to tourism for a kind of CV but culture by itself needs to hit harder and become a way to control and influence civs...science does this through increasing military techs but culture really doesn't...which should change.
Since in your model Tourism is a significative part of Culture output and this influence loyalty and immigration, then your population would end moving to live on countries with huge tourism atraction. This seems OK since in reality people moves to live to someplace after a nice trip, BUT by far most immigration is derives from misery, people seeking peace, freedom, jobs, etc. And apart from natural disasters the reasons to leave their homeland (includead war) are related to social classes, religion and heritage.
By the way most natural disaster before late game would be random and unrelated to player actions, unlike war, religious persecution and lack of jobs that can be controled by players.
Finally you make it look like if cultural influence is one direction when is in both ways, immigrants also influence the culture of their new homeland. That on game could mean new bonus for your empire from those immigrants.