the one person with the major solution was Joseph Smith. (No I'm not Mormon and never attended one of their services). Smith planned to run for president on a platform of freeing all slaves by selling off the Western territories and using that to buy the freedom of every slave. It would have satisfied the Southern plantation owners as they had major investment in slaves. It would have ended slavery peacefullly.
You won't find this in any American history textbook. But it's real history. They killed Smith's chances, by killing him. he had major faults, as did Mormons on gender issues, but one glimmering virtue was the Smith position on slavery. Had he become president, the politicians would all have lost and major bloodshed avoided. Other than Smith, no politician had a clue how to avoid the Civil War.