AD and AP versions of the same champion
I would find extremely interesting the idea of having 2 versions of the same champion. For example. Building ad Garen would look like a physical type of human whereas building him ap would look like a more magical version of him. His abilities would change entirely or maybe color, particles and of course dmg. This would apply to each and every champ. is this going to arouse you or disinterest you? Let me know. Edit; This might turn the tides in many game scenarios and of course, lore.