If SWU's for all Platinums is just too much for CO to handle, why not offer all Platinums a pair or two of a "capacity-control"-blaster certificates... that allow Platinums the ability to upgrade 2 1-way segments to J as long as a J seat is open for sale. Standard upgrade procedures would follow, but rather than hold back J seats for an eternity (and through the 72 hour rule), CO's best customers would be able to get a mileage upgrade when they want one ...at least 1-2x.