So Kozma's inventory is supposed to have mediocre general-purpose equipment. We get the Valiance, Levi and Nitronome, which are all general-purpose normal-damage weapons just swimming in mediocrity.

Then we get the Azure armor set and Aegis shield, which pass the "mediocrity" test with flying colours, but are clearly not general purpose as they're piercing-defense.

I think the Plate line would be much more appropriate for Kozma to sell. It starts off as pure normal, and branches at 5* to add piercing or elemental. Unlike the Azure/Aegis set, it passes both the "mediocrity" test and is the closest thing to general purpose armor in the game.

In particular, I'd suggest that Kozma sell the Volcanic line if only to avoid any dissonance with the description of the Ironmight shield.

Not only would this make Kozma's inventory make more sense, it would open up the possibility of buffing the Azure set to not be so uselessly mediocre.