Being in France, do you have a French Amex account? Because on QUALIFLYER, you can upgrade from most mileage earning fares (and the RTW is one) on CX to Business Class oneway.
Most European Amex membership rewards allow transfers to QUALIFLYER. If status is not really of importance to you, you might want to consider accruing mileage on QUALIFLYER (or to be renamed SWISS TRAVEL CLUB next year). You may accrue mileage on most Oneworld partners (even though SWISS is not a partner [yet]). You get 100% on CX, QF, AA flights. BA is to become a partner eventually by next year I think.
[This message has been edited by Guy Betsy (edited 12-09-2002).]