If the game is going to be Metroidvania-like, then equipment should do more than just inflict damage. Otherwise it will be too easy to sequence-break and/or go into a high-leveled place on accident.
Of course I'm not asking for the game to be linear. But it would be cool if Fire tomes also lighted any torch items, or if a high-ranged weapon was needed to advance through a certain blockade by hitting a far-off trigger.
Maybe Ice can freeze dangerous liquids and help you traverse over them. Adds a bit of puzzle-solving into the game too.