On JP the person that runs the swap shop runs 3 Crafting Shops where you can trade up lower mats into higher mats, get the free furnishing items for boost success rates, and Reset Discs that remove the customizations from techs and PAs (and yes, there are cases where you want to reset that, such as Ilfoie for damage).
These are all missing on EN.
The inability to trade up lower tier mats into higher mats also means that SPECIAL UNIT EXTENSIONS CANNOT BE DONE. Turning Saiki into a 60 attack 55 PP set is impossible because you simply cannot get the materials for it, as they require gold unit materials, but the highest you can get is silver for units.
The above also affects crafting of ultimate specific area Timed Abilities. You need gold unit materials.