Thing is, this would be the first major US airline to do this (not counting WN etc since they don't fly intl), and you just know that the implementation would be screwed up something awful.
Delta has already accounted for having a lot of elites and giving a lot of miles out... redemption rates for low level awards are practically non-existant and they've gutted the upgrade program with FCM for domestic and very high M fares for intl.