"AC . . . International upgrades can only be done using the limited number of coupons provided to upper tier members. These can only be applied to Y class international fares."

Actually, it is not a limited number of coupons--I generally have leftovers at the end of the year since I mix international travel with domestic so get sufficient coupons (sometimes with the help of a few friends) to cover all my flights. International and domestic flights can be upgraded for top elite (Super Elite) flyers from V or higher fares which is still a great deal. Elite (middle tier elite) can upgrade domestic from V or higher and international from Y/M only.