I have had some luck with a help agent do something similar while booking tickets on Cathay with AA miles last year.

1 RT / 1 one way on one account (for 202.5k); 1 one way on one account (for 67.5k).

I did have to try a couple of times to find an agent that would do it (the old if you don't like the first answer, hang up and call back rule came into play).

Good luck.