Since it is possible to book one-way awards at half the miles, simply ask for two tickets. The return in 'affaires' can be issued as an e-ticket, as travel is all on Air France. And then you'll just have to keep calling (annoying, I know) about the outward leg until they issue it as a paper ticket. But the idea that you can't mix Air France and Delta is ridiculous.

Don't they know that they were both members of same alliance? Sky something or other. I'm sure seen that somewhere