"developed skills"
I mean, that's a weak argument for them to make anyway. The only ones to benefit from this new skill are the owners, not the slaves. Hard to say "I learned how to harvest cotton well" is worth being torn away from your family and brutalized repeatedly because they've decided a whole group of people are just property.
I'm glad the Confederacy lost the war. But I fear that it will, after all these centuries, win the peace.
Some alternatives to Unity with:
And Unreal, of course, if you trust big corps.