The only thing that isn't really possible at the moment is to have "charms" using OtherDrops - items that, while being in your inventory, would grant you passive effects.
Together with the lorenames, this could lead to an awesome array of new possibilities.

Basically, the only thing that's needed is a performance-effective condition to check whether the player has an item with specific ID and/or lorename in his inventory.

You could make a "Vampire's Charm" that, as long as you carry it around, would grant you a 2% chance to steal life on hitting any living entity, a "Coin of Greed" that gives you a small chance of dropping gold nuggets, and so on.

We've got lots of "active" items on our server using OtherDrops (poisoned bows, grass-growing staffs and the like), and having Charms that let you choose between more inventory space and passive abilities would just be another great addition.

I would LOVE to see this too, I use another plugin to accomplish this right now but its lacking a great deal of features that OD can provide to support such a condition.