I've said this in another thread and it's worth repeating here.
This forum is about game design, not historical analysis, as interesting as that may be (I mean that sincerely. It is interesting).
So let's circle back to how things could/should
I just now noticed this post. Sorry.
However, I will say that if you intend on creating a strategy game based on as historically accurate issues as possible, then it follows that "historical analysis" would be necessary in a discussion bout how things in the game could or should be.
These are facts, most of which have been down voted for some odd reason, and absolutely should have a similar mechanic in-game:
1) Slavery absolutely has had an enormous impact on human history. This should go without saying.
2) Slavery absolutely DID have long-term negative consequences on ALL societies involved in the trading and enslaving of sentient human beings. And those negative consequences have had enormous and long-standing impacts on human history, as well as decision-making. I'll give one obvious example:
Decision-making:
Does Britain "side" with the North, the South, or remain neutral in the US Civil War?
The South tried to use cotton and economics to sort of "bribe" Britain to support their endeavors. Britain had other major sources of cotton in Egypt and India.
The North had grains, as well as the moral superiority. The British people were HIGHLY offended by what they derisively called "that peculiar institution" in the Southern US states.
The Northern States also had a superior navy over the South, and for the British to have to contend with a growing naval power would have been expensive. Just to support an offensive slave-holding society that doesn't even offer them any sort of real economic incentive to do so. Other than the fact that it would have permanently divided the upstart rival USA.
The British remained neutral. And slavery was one of the major key causes of it. How much different human history would have been had the British interfered in favor of the South!
That's not even to mention the cultural impact the Africans had on US society:
Food, music, language, the arts: clothing styles, acting, etc. Politics, economics.
The history of slavery is completely intertwined with the history of the United States of America. The USA, in turn, is among the most influential nations in the world throughout the 20th and into the 21st century. The ripple effects down through the centuries and all around the planet among human societies is extremely far-reaching and undeniable.
If you want to create a truly immersive and historically accurate game, you cannot just simply whitewash and ignore such historical analyses. After all, that's why the game includes such systems as the HRE in Europe, the Mandate of Heaven system in China, and the Daimyo system in Japan. These are extremely important institutions that have a great impact on how the game plays, and adds a depth that is unparalleled in the strategy gaming world.