SCL is tricky given that AC only serves YYZ from there. However, AC 92/93 serves both EZE and SCL (seasonally anyway) so using AC to hop across the andes to EZE would be possible.

No matter what you do, going via the USA will double (or maybe worse) the length of your journey, probably resulting in being charged for Z4-Z3 and Z3-Z9, which is a 50% increase in miles required over a Z4-Z9

The only valid route I can imagine would be acceptable would be with South African, travelling EZE-JNB-PER on SAA, you'd have to make your own way from Perth to Brisbane. SAA do actually codeshare on Qantas JNB-SYD which would be better for getting to Brisbane, but this obviously won't be available for redemption.
Distance wise (by great circle mapper) this comes in at just over 10000 miles whereas a direct EZE-PER would be 7800 therefore I'd think this reasonable for a Z4-Z9 direct, plus it appears in the *A timetable which also backs up your case.