Certainly worth a try, but on the DONE4 I've just booked, AA's agent happily accepted a QF flight but by the time it had been into ticketing and come back again, it had been magically changed to an AA codeshare on the same flight, without asking me. So if the agent agrees, check on the website a day later and be sure it has stuck.

Other than that wrinkle, by the way, I found the AA RTW desk to be super professional, helpful, with a decent sense of humour too, and willing to work through all the details until the journey is right. Far from the usual call centre experience one gets with airlines these days (if indeed your favourite airline still answers the phone *at all*).