Your posts are well-crafted to solicit suitable responses. Let me turn it around on you. What do you think it would have taken for the North to let the South peacefully co-exist? The North was beating the war-drum in 1861 and it wasn't to free slaves.
A good question,and I'm not about to argue that the North fought the war to free the slaves. But I doubt that there was any other issue that would have led the south to secede, to raise armies, and to fire on U.S. troops at Ft. Sumter. But, at the simplest level, I think that if the south had simply stopped demanding the expansion of slavery into new territories, the north would have left it alone. I think that the south demanding the Missouri Compromise of 1820 be overridden by Kansas-Nebraska act was a mistake. I think that demanding an enhanced Fugitive Slave Act was a mistake. And I think that those actions made it possible for hardliners on both sides to come to the fore, split the Union and take us to war. Of course, I also think that dividing the Democrats among three candidates in 1860 was suicidal against Lincoln.