Create a new type of storage - Dresser. Unlike any other storage it should allow to store only one set of equipment. But instead of manually storing/retrieving items it should allow to store all current characters equip or retrieving and equipping it.
It will allow to transfer equipment smoothly between your characters. Probably should v 0 or 1 such storage available by default. And more should be unlockable via coupons. Could also have two version - per game account/per master account. Could be implemented via different npc/line of npcs