I would have Nintendo and Sonic Team work together (If Sonic Team said yes, witch i can probably say won't because Nintendo has something up there a$$ all the time). It would be a RPG. The next line of games (like the golf and tenis, and kart series). It would be like Mario and all the good guys from Nintendo (Laugi, Peach, Toad, Dasiey, Donkey and Diddy Kong)teamed up with all the Sonic good guys (Sonic, Tails, Knucles, Cream) and would try to save both the mario and sonic worlds from bowser and Dr. Robotika and all of the bads guys from there (Wario, waluige, Shadow etc...)