Unfortunately all the LA flights from Buenos Aires to Patagonia fly out of AEP so if you wanted to go to somewhere like Ushuaia then you'd be looking at LHR-EZE,AEP-USH-SCL-... which would still allow you to visit IPC but the airport change takes up a sector, which is frustrating.
If I were to do this crazy thing, I guess I would also have to figure out how to book a flight ex-ICN. I assume that really does require a travel agent, although I would actually be flying AA metal on this one so I suppose using the RTW desk would be OK. Any leads on what S. Korea travel agent I would use for this kind of thing?
I'm fairly sure that you can book xONEx fares ex-wherever, in the currency of the departure country, using the online booking tool. Just plug your desired routing in, select flights, and the tool will give you a price. When I recently put in an itinerary ex-JNB the quoted price was the one displayed in ZAR on the oneworld website, despite my Australian IP.
Also, for mucking around with routing and destinations I thoroughly recommend getting a copy of AirlineRouteMapper (search for it on Google). I find it invaluable for planning trips .. now all I need is the money to actually go
And while I'm at it . . . if an xONE3 goes ICN-NRT-(North America stops)-(Europe stops)-HEL-BKK-HKG-ICN, is that kosher if the stopovers between BKK-HKG and HKG-ICN are each less than 24 hours? I wouldn't plan to use the last two segments in any event. Mileage Monkey says OK, the OneWorld online booking tool gives me a "warning": "You have already used the maximum of two stopovers in your continent of departure. You can only make an extra stop if it is less than 24 hours." So . . . OK?
That should be fine, once you select the flights BKK-HKG-ICN the warning should disappear.