Maybe make specific crafting bell for that purpose. It would work just as regular bell, but also have the storage sharing ability. Add it into only one place in a city so the crafters can stay annoying each other while others can use the other balls. And make it a housing item too, or maybe even just housing item not existing anywhere in the open world. Now with the apartments available practically everyone can have a room so as such it wouldn't even be restricted to FC members and house owners anymore.