4X in space, you conquered a planet and there was alien population. What to do with them? I was thinking and the most logical would be to assimilate them into Empire as lower status citizens. So, the player would have an option to set the level of citizenship (full, limited, no rights, slave) for each race in the law panel and it would affect all of that race pops that happen to be inside your Empire for whatever reason.

To simplify: I'm excluding all strange races and assuming all are humanoids of some sort (only humanoids can be integrated, all insects, bugs, etc are exterminated upon conquest).

That's the core idea, if you have anything related, speak up. Note I have no specific question, just would like to explore this alien citizens concept.

I think each type of alien should have a sliding scale associated with them measuring rebellious nature at one extreme end and cooperative nature at the other end of the scale. Depending on the scale this should depend on how easily you are able to enforce your will on them, and the more draconian your policy the more likely rebellion will be. Rebellion will cause you to have to spend more on local security etc.

Giving them full membership should influence your government with their culture in some way e.g. by making it easier to aquire and integrate their technology into your research trees etc.

What do you think?

I was thinking and the most logical would be to assimilate them into Empire as lower status citizens.

For me this has some kind of bitter aftertaste.

I think that there are other, more modern ways to handle this. Like a big ferderation with autonomous members which have different attributes. Like loyality, economic power, military power. The releation of a member to your empire/federation could be well-disposed, aspirant, loyal, core member etc. which imply different advantages to the federation and to the member itself.

I think you have to pay attention with this. If I understood (reading your past posts) you would like to avoid micromanagement at all. This aspect of citizenship seems like something that could easily explode in your hands with lot of options -> micromanagement. A simple "set the level" is the best option perhaps.

If your empire as a whole had different ideologies as a choice (kinda like a character class system) then this would be cool.

Different idideologies/classes would be offered different options in situations like this.
More prejudiced ideologies would have the option of genocide, slavery, apartheid. More compassionate classes would have other options such as giving up land to the natives (loss of production, but less rebellion), more equal assimilation (which may lead to racial tension if the population itself doesn't share your ideologies), etc...

Rome Total War had three options when you conquered a region. Briefly, you can keep population (takes time for happiness to restore but keep full numbers) , you can exterminate population (most of barbarian population dies, less resistance but ends with region with low workforce) or enslave (disperses population among other cities, increases workforce at other cities but also lowers happiness due to cultural clash)

So it can be something like it. You can also have option simply to change ruler of planet and give them autonomy but require their presence as taxation and troop supply when needed.

Don't forget the interesting aspect of what happens even within the superior race(s) of your empire. Refusal to airdrop the disease-infested blankets on colonized planets; citizens caught selling intoxicating rocket fuel to lesser species on the reserved wasteland left to them on their native planet; breakaway planets forming an alternative federation and eventual civil war over freeing the slave races; million-lightyear marches over the lack of civil rights for the disenfranchised species; organized crime including intoxicant running and illegal planet-hopping among the second-tier species; space police violence and subsequent species riots; lynching poor refugee insectoids from their own spinnerets after accusations of stealing your women, etc.

Maybe you're just better off wiping out every alien species where you find it.

I was thinking and the most logical would be to assimilate them into Empire as lower status citizens.

For me this has some kind of bitter aftertaste.

I think that there are other, more modern ways to handle this. Like a big ferderation with autonomous members which have different attributes. Like loyality, economic power, military power. The releation of a member to your empire/federation could be well-disposed, aspirant, loyal, core member etc. which imply different advantages to the federation and to the member itself.

Federation can't be easily implemented into a more or less traditional 4X, you need to conquer planets (and when you conquer a planet you suddenly end up with millions of aliens and you need to do something with them - genocide being uncool :)). Plus, I think federation could be done much better from scratch (not as 4X), check "The Last Federation" for example.

Anyway, even if, what about aliens living on another planet that has your race (multiracial planets)? Which is kind of a basic scenario, in real world aliens do not live on their planets alone, they always have some tourists, immigrants from other races and so on. Even if there is a federation system, it does not mean population would not mix (especially if we talk about them all being humanoids; come one, wouldn't you welcome some gorgeous Antarian girls in your homecity? :D).

The thing is, when you conquer a planet (and you do it a lot in 4X) you get planets with inhabitants. And... we need to think how to handle this scenario. It does not even need to be about political struggle, population happiness, etc (of course it could and probably should). But first I wonder how they exactly mix (can they use the same factories, what happens if there is food shortage is your original race starving equally to the conquered slave-immigrant aliens?)