Decided to redesign mostly Shadow for my Sonadow fanfic In a Dark Ablaze. I just wanted him to look more monstrous. Sonic isn't a monster or alien, so I just give him a newish outfit.
You can follow the pillowfort link on my page to read Ablaze and each chapter contains a link to the AO3 post if you prefer to read it there. These new designs will obviously start in Part 2.