Armoury Chest

[Mjollnir]

And having it so you could have a gear set for the class and job is redundant, too, since only the job gear set would require it.

How else would you be able to tell the game you wanted to equip the job instead of the class? It's not redundant, it saves having to equip the soul crystal separately after changing class.

Only thing it would really be useful for is for multiple gear set for the exact same job, like I said with DD-WAR and Tank-WAR as an example. WHM and DD-WHM gear sets as another.

There are some occasions where you want to go MRD instead of WAR (for instance), so having the soul crystal slot as part of the Armoury Board would enable that.