@FlyingFish: I looked at the numbers. Assuming starting from zero status on AA, after four RTs YYZ-HKG-BKK on CX, you will get to AAdv EXP elite status and will have 135k AA miles, enough for one F award ticket, along with 20 domestic upgrade stickers, and 8 systemwide upgrades. Each additional RT as an EXP will get just under 40k miles. Yes, all those upgrades are only good on AA flights and your priority for op-ups on CX, even as a top-tier EXP, will be lower than if you were a DM, but they aren't zero either.

Definitely, shorter overall flight times and avoiding unnecessary border crossings is a good thing though!