https://limewire.com/d/STLYY#J4e0mrDGPh
This is just a simple mod so you can play as Latias and Latios in Super Mystery Dungeon. Latias replaces Pikachu and Latios replaces Riolu.
Let me know if you run into any problems. Main problems I saw when doing a quick run up to chapter 3 was mainly related to Latios not having some portraits available to him in some cases or Latios being so massive that he'll just clip Latias into himself due to not knowing personal space.