What's a war 3 hero? A unit with experience bar, team glow and abilities that have levels. There's already an inventory ability for units or a hero-inventory that can be added to a unit. The thing with SC2 is there won't be items... they won't have to balance heroes and items. Still, a unit can be made a hero using other systems like after gaining some points to have increased mana, hp. Then you can always replace an ability with a stronger of the same type called level 2. Items can be made like a unit with model of an item. With triggers you can do all add skill/remove skill, increase hp/mana, when close to a unit with model of an item to add a buff or time, etc it can be done. But I hope they don't bring war3 units to SCII coz such mixture will suck. With the limit of units they allow, there will be indeed Defender Of The Future-s!