LOL, would be fun to get them to try to ticket that JL coded LAX-SCL. I seriously doubt it would stick once it went to ticketing and someone knowledgeable with xONEx saw it, but you never know. I think that's where you're seeing BA may not be as good to ticket this with as once thought since you're not getting to a real RTW agent like you would with AA. Might involve more back and forth to negotiate some mistakes like that before you can get a ticket they're willing to issue.

AA actually used to fly to Brazil on a 787 from LAX pre-COVID but that is not likely to ever return. For anywhere else in South America you'll need to go from MIA, or on a few routes there are DFW and / or JFK options as well. SCL does have DFW flights.

In terms of the cost increase I forget the incremental difference between a 4 and 5 ex-OSL but usually it's not too much, I want to say ex-TYO it's about $800. If you want to go to South America and you're not going to do these tickets on a regular basis then it's a good add on. It's still far better than you're going to find a discount Business class fare for from North America usually, and those while sometimes under $1000 are short lived and limited dates. (ex-CAI the incremental cost between 4 and 5 is almost nothing so it's almost silly just to ticket a DONE4 from there.)