Technically any OW carrier can issue this ticket; most are reluctant unless they have the trans-oceanic segments. QF does a pretty good job issuing these tickets, I would not hesitate to have it be issued by QF and you don't have any rule nuances in your routing to finesse. Your most likely to be changing the QF sectors which may be easier with a QF issued ticket (also CX is competent at dealing with non-CX issued tickets). AA would issue it as an e-ticket which I personally do not like, having twice been refused boarding when my e-ticket was not in the system, and the onus was upon me to prove that the ticket existed and I had a valid reservation (hint: PNR is not enough, you must also have the ticket number memorized).