The Union was not trying to fight for emancipation but to preserve the union. True, but it makes one stop n think when they read the rhetoric flying around during the campaign for the presidency just before the war. The debates and speeches were full of the word 'emancipation'. As much as one would believe that preservation of the union was the real cause, it's not easy to ignore the sideshow. It was very much a part of it. The Union may have hauled him into court and disposed of John Brown, not because they disagreed with his stand on slavery, but they could not abide his terrorist attacks. He went too far. Had he waited, he could have joined the Army and gone on his killing spree and been paid for it.
I know you can't mix apples and oranges but there's some fruits that are cross breeds and sell very well. I think this period in history we've been talking about is sort of like that. The Union had an answer for everyones concern. Official stance may have read one way but those who read the fine print could be satisfied that the 'other' matter was very much in play.
As for the Confederacy using slaves as soldiers? I still think that was a bad idea unless it was used in the beginning. Then again, had they done that in the beginning, it would have saved a lot of people the time and irritation trying to deny the Confederacy was all about saving slavery. It would have been the one way to show the Confederate States wanted to be emancipated from the United States. Guess timing was everything on that little matter.