You should note that the only airline programme that has the most upgrades and on a oneway basis (helpful if you're on RTW tickets) is ASIAMILES.

AA permits upgrades only on CX and only when booked in J class, and on a roundtrip basis.

BA doesn't offer any upgrades as yet.

CX's ASIAMILES can offer upgrades on CX, AA, BA on most fares including RTWs and they can issue oneway upgrades too.

Trouble is getting enough points in ASIAMILES for the upgrades.