There were anecdotal reports of AA stopping ex-CAI tickets, but then a few people came back later and said they've had some issued recently. So YMMV but it's worth a try and perhaps even a HUCA.

From personal experience and others who have dealt with QF, just don't do it for a RTW. Changes are painful as it's really hard to find an agent who has any clue what they're doing. Most calls get routed to Fiji which seems to be their most incompetent call center. I did have a lovely representative in South Africa once who was pretty awesome, she knew nothing about the ticket but took the time to learn and got everything done in a few hours. If you get lucky enough for Hobart (which seems rare) they are also suppose to be fairly good, but when I would call I'd get Fiji like 90% of the time. In the end the only way I could get anything done was using QF's social media team (I used Twitter, but another poster mentioned FB Messenger too). They actually have a clue and get things to the right people to get them done but it may take a day or two.

BTW, if you go via the OW tool online and your first carrier is RJ to Amman, my understanding is that QF is the ticketing airline, so definitely find a travel agent or try AA.

I just ticketed my most recent one with CX and have heard mostly great things about their ability to service the ticket later as well. I have only had the one experience making a minor change to a codeshare before ticketing, so can't say firsthand yet. But whether you can get CX to ticket or not depends on your itinerary, they like to be the first carrier on the ticket but have also heard at least one person say they've gotten CX to do their even without being the first carrier.