There are certain items for certain characters that I think are ADORABLE, but aren't permanent. Either that, or the character lacks almost anything that is permanent. (For example... Maki only has a permanent hair other than her Korean set. Example #2: Kai literally doesn't have a single permanent item.)
What I'm suggesting is that Prizma adds, somehow, the option to buy certain items permanently. (Such as making Kuro and Yuki's ninja cash sets have a permanent use option.)
This could also possibly be accomplished by adding in alchemy recipes for these items that require the item from the shop in order to make. Sort of like how you need King Panda gloves in order to make Mountain King gloves.
I'd add a poll, but my 3DS doesn't support the poll making function of the forums.