Just an idea I came up with. It could start off as a random forest event and when you first get there, it will be a simplier version of Orochimaru's hideout. After you get through, you have to fight a a few (as much as I hate to say it) Ninja Cats. They'll be harder than Oro, but possible to beat (not as hard as the ghosts).
Once you beat them, you are able to deposit items, and buy items (like shuriken and temp hp potions) at prices higher than the other forest event (high enough to cancel out the ease of buying them). Once you get through it the first time, it becomes possible to go directly to it (like the Curry Place, but with all mounts), and pay a cat a certain price to guide you through the place (you skip to the end, and don't die).
Obviously, you won't be able to buy Perm HP potions, or items that result in events (*cough*Rasengan*cough*), but you'd be able to deposit said items.
And they would be exclusive to that character, so a person wouldn't be able to take an alt's items, something that Neji would consider.