If it was me I would of made something like. (if they are going to allow any class to be able to repair)
  1. Actual crafting class to repair - repairs up to 100%
  2. NPC repair - repairs up to 99%
  3. Other class repairing using repair items - 50% / 75% / 99% (depends on repair item used) - any class can repair but not as much as NPC or original repair class.