Here are the options:
1. Exactly as they are. Remove the existing CM's and their gear from being attainable.
2. Remove the CM's, but like the mounts, make the Armor account-wide, allowing someone with 9/9 Golds to get all of the Classes' armor.
3. Allow the existing CM armor to be earned in the new CM's, either in addition to or as an alternative to the new CM armor.
4. Further downscale players running MoP CM's by disabling all lvl 91+ abilities, and also tertiary stats.