I just did this in October. I had a 20 segment paper ticket with 12 flights remaining.
I called AA RTW office and they said the rule is "once a paper ticket, always a paper ticket." However, if the ticket needs to be re-issued, some check-in agents may change it to an e-ticket.
So, at JFK F check-in where the ticket needs to be re-issued due to routing change, agent calls RTW office for instructions and is clearly told that it must remain a paper ticket. However, agent has only one paper ticket (4 coupons) and needs two more. So she is hunting up and down all the counters and agents trying to find more, and eventually a super comes over to see what the problem is, and says "don't bother with paper, we'll just make it an e-ticket." Which they do.
Whole process took about 45 mins so make sure you have plenty of time if doing it at check-in. But be aware, that it seems to be hit & miss if you can get an agent to convert it to e-ticket.

Heading off next week on a new 20 segment AONE5 from JNB, so I will be trying again in a few weeks after flying the first 4 segments.

Happy Travels.