You know, all this got me thinking about some things... And I've decided to add some ideas.
1. List-based inventory: Not all games have grids with icons for inventories. Some games, such as pretty much any JRPG or the recent Castlevania games have list-based inventories with either one or two rows and scrolling, with the games of items displayed instead of graphics, the graphics normally being displayed when the item is highlighted, along with an item description. Surely that can be easilly interchangable?
2. Equiping items: Pretty much. You want to allow the player to equip items of a particular attibute and only one (or two, etc.) of these? You can double-click or move an item to the equip slot and if there's an item already there, that item will either return to the inventory, or if you don't want to move items from the inventory to equip, just simply update the equip list. This could also be expanded in case of multiple characters.
... Thinking about it, we need an RPG stats plugin or something like that to handle that sort of thing, it would compliment an inventory very well.