Simple idea for a new line of items, not sure what exactly to call it except this.
The new items would have a base recipe and then an optional item choice that changes the stats. I'll use Guardian angel as an example of the concept, right now the recipe for GA is a chain vest, null-magic mantle, cloth armor and gives you 68 armor and 36 magic resist. If GA were to be a new item with this concept the recipe would be Cloth Armor, Null-Magic Mantle and then you can either use a Chain Vest or a Negatron Cloak. Using the Negatron Cloak would alter the final stats to give more magic resist and less armor. Items with this feature would have to be slightly reduced in power to make up for the additional gold efficiency.
Im in no way saying that preexisting items should have this feature just an interesting way for a few new items to be able to be introduced into the game with something unique that doesnt eclipse items that already fill a role. The only downside i see is that if the stat choices available arent balanced appropriately it would lead to making other items never purchased because of the more optimal stats you could potentially gain.