Many multiplayer games with streetpass save a copy of the character for whatever thing the game does. eg: Animal Crossing save the person's house, Mario Kart lets you race against their current cart, Mario Tennis saves your Mii's set up and allows you to have a sudden death match and play ring shot. I could easily see XY saving the trainer's team and allow you to battle an AI version in a building or whatever. Sort of like the IR Battle House in GSC or Mixing Records in RSE but passive. I'd also like to see implementation of some sort of Pokewalker-like thing. Either an in-game thing or a separate app. The 3DS has a pedometer, please use it even though no one else does!