Compared to the $11.6 billion dollar cost of the war?
"Not practical" in the sense that, Quincy Adams's power play having been set in motion, you would never have convinced anyone involved it its realization, not John Brown nor any of the Secret Six, not Abraham Lincoln or any of the governors he spent hours locked in secret councils with in March and April 1861 -- and evidently before that, too, given what happened in e.g. Missouri -- nor any of Lincoln's cabinet at any time in the last 10 years leading up to the war, nor any of the leading Abolitionists, like Wendell Phillips, the Beechers, and Frederick Douglass, that a huge outlay of treasure such as you suggest, assuming your numbers arguendo are reasonably close to a sale value, would be worth the expenditure to forfend the coming hecatomb.
By that time, I think group-dynamics students would tell you, the players on both sides were already heavily invested in violence -- "martial law", "reorganizing the Southern States", "defending States' rights [and we're gonna whoop 'em], or pick your euphemism -- and ready to go to war after years of mutual recrimination, suspicion, aversion, and plain old hatred.
By the way, one of the more active areas of ACW studies in the last 10 years has been research into Abolitionist and Unionist propaganda and the way its dispensers used it to foment the war and foreclose any chance of reconciliation (such as the language with which Popular Sovereignty, Lecompton, Dred Scott, and the Constitution itself [famously, by Garrison] were reviled in Northern States).
Eventually Southerners were using similar language, and at that point -- the trial of John Brown -- the Union was over and the molten mass of People and their melting institutions were ready for Lincoln's and the industrialists' hammer.
So what I mean is, even on a fair showing of comparative values, at no time after Lecompton, say, would a proposal of redemption and emancipation, even if fully capitalized, stand a chance of acceptance by both parties, who were on the verge of seeing the arbitrament of the sword, to borrow Longstreet's words, as the superior mechanism of settlement.