Can't agree, once the die was cast the North could not end the war by anything other than victory or defeat.
Whatever the South's motives, the North was fighting to regain or retain the geography and to institutionalize it's dominance over the resources of the South.
I do not see how these two statements are in disagreement:
My statement: "..if the offer had been made mid war, there may have been a different outcome."
Your response: "Can't agree, once the die was cast the North could not end the war by anything other than victory or defeat."
My statement indicates the (by no means certain) victory for the South and so does yours or did you slip in the words "or defeat" to confuse me? :-)