Note that for the Platinum Challenge you need to fly either on AA metal or on an AA code on a partner. So for example, if you want SFO-HKG-DEL/BOM on CX metal but using the AA code (just the SFO-HKG part; no AA codes on HKG-India) you'd earn over 10,000 elite qualifying points on the outbound HKG flight, and land in Hong Kong as AA Plat. You'd earn 100% bonus redeemable miles on that flight and all subsequent flights on most Oneworld carriers (the exceptions are Malev and S7 I believe) so not bad.

One thing to note, however, is that Plat on AA doesn't allow you to use AA lounges on domestic itineraries, so if you reach Executive Plat or else decide to try for BA Silver on subsequent trips, your BA card would let you into Admirals Clubs on domestic flights.