A general tip is to have only one account per alliance. You are almost there. If I were you, I'd out all future OneWorld miles into BAEC and all future SkyTeam miles into Northwest. Assuming you travel at least a little regularly, I'd leave it at that -- you lose way too much from airline to airline. And I don't think there is a good way to get Delta miles out. When mine expired, they let me get magazines for them!