This has been wanted for a very long time by a large number of people,. hopefully they do it.

I just want to be able to liberate a previously-conquered world and return it to its rightful owners for a diplomacy bonus. That would be cool.

That would be an interesting idea...

-Allow the remaining populous to join your citizenry - +10 Benevolent and Population bonus (remaining troops + 25% planet population upon invasion)

-Enslave the remaining colonists - +10 Pragmatic and Production Bonus for the planet

-Exterminate the existing populous - +10 malevolence

Every time you settle a planet you get these choices. Why not have these choices upon invading a planet (or varients)?

That right there is a perfect example of an incredibly easy way to implement that. And you did that entirely off-hand.

So let's work on that more, focusing on the middle two.

I'd love to see the ability to actually have multiple populations on a single planet: Such as the invader and the invadee, so to speak. So for instance, let's say you conquer a planet and they surrender with 25% of their population remaining. Fold that into the total population of the planet.

Now you've got your three choices, as Parrotmath outlined, and what to do. Bring them into your citizenry (probably takes time, as I mentioned), enslave them (maybe they can't be taxed or research but, as Parrotmath also brought up, contribute directly to production in a BIG way?), or simply eradicate them to eliminate the complexity of losing taxable, researchable population or having to worry about social issues from integration, and the universal issue of rebellion.

Boom. You just brought Galactic Civilizations 3 that much more to life in a big way for comparatively little effort in the grand scheme of this game.

Well, really, all this actually adds to the game is the following:

Three options after you successfully conquer a planet. One population pool per species on a planet.

How much more complex it gets than that is up for debate. I like my TBS 4X gameplay to be very big picture--the less minutiae the better.

However, I feel like this is the very sort of big picture decision I'd like control over.

It also adds a fun layer of "Well I'd love to bring them into my population but they're robots." when you conquer people you can't assimilate or can't enslave, removing the option that you might actually use a lot. So much you could do here and it seems like a massive missed opportunity.

All of that is an excellent point. This could get crazy fast depending on how deep you go with it. That very possibility is why I mentioned that you would need to make the decision very carefully as to how far you let it go.

Features in games, especially ones like this, are a delicate balancing act of work required and the gain.

Honestly, I think the ideal for me would be something like this.

You conquer a planet and make your decision. If you integrate them it takes time for the populace to assimilate, at which point they share the sentiments of any of your other citizens--for the most part. If you enslave them they don't contribute to wealth or research of a planet but contribute far more than normal to production. If you eradicate them, well, that speaks for itself.

The next, and only other, feature I think would be a neat would be the potential for species-based uprisings should morale get too low. This gives incentive to keep your morale extra high should you be big on conquering other species and bringing them into your empire. Slaves will revolt and fight en masse, assimilated species will not (representing those few not truly comfortable with living under your flag).

I think something like that is great. You don't need to worry about the minutiae, I know I wouldn't want to. But it does add value to other aspects of the game (such as morale, as I just outlined) on top of the expanded diplomatic potential. At most it's a multiple choice question and remembering "Oh that's right I have a bunch of pissed off Drengin slaves here so I should make sure the general populace stays happy and can keep them down."

Simply having a record of there being a considerable alien population would suffice, honestly, in order to provide the aforementioned "You liberated our people and now we love you long time" sort of situations.

See what I mean?

I wouldn't want to worry about the actual intricacies that would be involved in something like that while playing a game with 50 planets. Because you're right, it should scale well and that's what I love about Galactic Civilizations as a franchise. I'm not playing a general, commanding battles. I'm not playing a governor, designing cities on each colony world.

I'm the leader of a galaxy-spanning civilization who's working with biggest of big pictures.

You said it very well, it must scale well.

I like the way in which existence of multiple nations in single city is done in Civilization 4. However, population there isn't used in battle and there is only one specie in that game. Taking into consideration all possible species (major and minor combined could easily number hundreds) and their cultural/political affiliation (also possibly in hundreds, one for each player) would easily make number of subpopulations on each planet in excess of 10.000 which is ridiculous.

Using only division by species would negate the possibility of members of one specie living on foreign planet affiliating themselves politically with the planet owners' specie governmnet.

Using only native and owner tags is not enough, I think, because what if the planet is counquered over and over by 5 different players?

Idea is interesting and it would be nice if someone could think od scalable, simple to use and plausible system, but maybe that is too much to ask.

I think it can't be meaningfully done without at least diving the population into subpopulations of species. Then they could be assigned status by each player for his empire, for example if I am A and I assing status to species A, B, C, D, etc. in several tiers:

1. Free - free and full citizens of the state (the state could still be feudal or monarchy for example, but the members of this tier would be the most priviliged in the state)

2. Underprivileged - free but without all the rights, no say in politics etc.

3. Slaves - used for forced labor, food, whatever the empire wants

4. Targeted for extermination - killed on sight

Default status could be locked 1. for player species and changeable 2. for all the rest.

Every specie could also have a global standing towards each player distinct from player to player diplomatic status in several tiers:

1. Loyal

2. Opposed

3. In open rebellion




I don't think any of this would significantly add to the depth of the game in the present from of the game but it would make it feel more real which may not be too important. The main problem I see is that you could always exterminate everyone (if you are not concerned with ideology and diplomatic status) and just wait a few turn for your people to overcrowd the planet because population growth in this game is ridiculous (sometimes billions in one turn). It would be necessary to make bonuses of having slaves or free citizens from another specie significantly more useful than just waiting a few turns to repopulate with your loyal citizens.
The bonuses could be access to special abilites or techs of that race (you can colonize aquatic planets easily with your loyal minor race sea monkeys but not with humans), diplomatic bonuses, manufacturing, culture, influnce, but IMHO they would have to be significant enough not to be easily dismissed.

Also if something like this is implemented, it would make sense to implement migration as a result of overcrowding and/or cultural/economical superiority, mixing of populations due to trade routes etc.

And also if it could happen that you can keep a part (let's say 25%) of planet population upon successful invasion, it would make no sense that the invasion is a fight to death.

For example, it could happen that you attack with 10B troops a planet defending with 20B population. It could happen that you could lose a close battle and be left with 0B troops while the planet is left with 1B population, but if you had just a little bit more luck you would win and be left with 1B troops and 5B of conquered defenders. That means that if you're more successful in killing the defenders they end up with 4B less casualties which makes no sense.

The fights to the death would have to be replaced with something else for this to make any sense if immersion is what it is aimed at here.

I think the understanding I have with a planet population of 20B is that all the people in that planet are not fighters, they only fight if pressed to do so. A person has a lot of courage, if they can be inspired by the right person, but if you are successful in killing the right people, then it would make perfect sense that these other non-fighters would give up and surrender.

When recruiting for an invasion force, I'm assuming these people are receive extra training and learn combat directly. Hence, all become hardened soldiers in the process.

In GalCiv2 you pretty much did that. When you invade, your troops (1000, e.g.) fight VS the planet population (8000, e.g.) you the corresponding bonuses and if your troops had the largest bonus, the planet is conquered, if not, the remaining population is proportional to the bonuses after the fight.

Just one question here. What about cultural/influence conquest? You actually conquer a planet, just not by militaristic means, right? what does happen with all that population? If I'm not mistaken the population was reduced to a fraction (more or less about the size of a colony ship at the beginning). And since they "surrender" pacifically you don't have unrest (it would be weird to have unrest). Also, you will have a planet full of, let say, Terrans, since you didn't kill any single of them. What uses do they have to the Yor those meatballs? Slaves? That would break the idea of cultural domination because, you see, I didn't wish to join you to become a slave so I rebel, again, or (the conqueror) I didn't want your planet if that means to deal with rebels, unrest, special cares and what not.

In this regard, if you put especial care to military conquest you also need to balance cultural conquest. Both of them are a type of conquest and both of them have they pros and cons speaking of managing population. Yor, for example, does not  understand the needs of a better type of government because all his people work as a hive-mind while it makes almost impossible to manage a planet for "organics" with structures that are specialized (not game wise, though) to interact with a cybernetic race. 

Game-wise would be way better if we do not think too much about the leftover of a conquered planet (by any means). Just think as all the remaining forces were extradited to the cold and empty space to fend for themselves and/or become part of another civilization/pirate group (pragmatic), not counted as population until they are brainwashed (the way of malevolence) or convinced that you are the nice and good guys and way better than those old folks you used to call "my government" (the path of the good guys). All this would be better as a cosmetic thing according to your ideology score rather than a way to gain bonuses for it.

Good to know, but, if they do not show in the statistics (population), how do you know that they do not contribute in the fight? Don't get me wrong but I feel like the enemy soldiers say: "all of those who are at age of fighting and has paid taxes come here to be killed, everyone else, just stay away" . 

Really?   [e digicons]'[/e]  It seems that I mixed all my info.