CO doesn't offer SWUs and IMHO they shouldn't offer them. Just think, any SWU is going to end up being capacity controlled just like the current mileage-based upgrade system is capacity controlled. Adding more complexity to existing set of rules is not the solution here. The real solution to this problem is to either do nothing (because there is no business reason) or, (if CO determines that there is a business reason to do this) to give SWU-equivalent mileage bonuses after some level of flying and to let the current upgrade system perform its magic.