i wish they'd move the outfits to the mog store and made veteran rewards earn crysta instead so we could pick something else from the store altogether. (i personally never touch the rewards)

failing moving the outfits for the sake of uniqueness or whatever, another idea: as a reward, add a Rank 5 (and above): each rank earns you an amount of Crysta, which can then be spent at the mog station or wherever else if you save enough.
Rank 5 would add 200 crysta, and every rank after that would add an extra 50~ (so, rank 6 adds 250, rank 7 adds 300, and so on, up to a maximum of 500 at rank 11, where every rank after will pay out 500 crysta)

i don't know how you'd choose to handle players who've been subscribers for a long time - either retroactively pay everything at once, or start from the moment the system would be implemented.