Blank Powders

During The Envoy Part I, you get 4 blank powder IV's, there is also an option in the powder exchange to trade with blank powder V's and VI's, however I have never come across these in the game.
Am I missing something? Or are they intended to be added at some point?

 

they exist as a way to exchange powders

for example, you have a T6 thunder powder that you want to exchange for a T6 earth
you give the powder and 1 LE to the merchant in the corkus powder exchange to get a T6 blank powder, which you can then exchange for a T6 earth

 

At the powder exchange, you can trade a T4 powder and a nii rune for a blank powder IV, t5 powder and an uth rune for blank powder V, and a T6 powder and an LE for a blank T6