I'm trying to find a good way to make an item usable (equipable) only by a specific hero. For example, so that a mage in RPG won't be able to equip a sword.
Any ideas or ultimate solutions that I'm not seeing?

I asked around in the sc2mapster IRC channel and someone suggested creating different item classes and inventories with slots for only a specific item class. That way they can only equip an item in a slot for that item class.