I literally was trying to find a fix myself for this problem. I got flawless on my Xbox account forever ago and put in too much time on PC now to just throw it all away for some emblems and shaders. Really wish they had some way to share progress - they literally have all the data for it and show it to you on your profile. Cross-Save is meant to have one account supersede the rest, but can be undone. The problem is that you can only progress one account and not share any earned emblems....even if they have the data and could easily do it. If there ever is a solution I'd love to have it, really sucks getting punished because a system didn't exist when I bought two copies of the game.