My opinion on Sonic characters has changed greatly from when this game was first announced. Adding so many Sonic characters kills the point of the crossover. Either way, seeing as there will obviously will be another Sonic character, I just hope it will be either the Chaotix, Cream and Cheese, Fang, or a Chao (though I'd prefer Cream and Cheese). Blaze's inclusion wouldn't bother me THAT much, but I'd prefer if she stayed away. Anyone else should just steer clear from the game.
Six characters really is enough though. I would honestly prefer less than that honestly, just the main 4, but I atleast understand that Amy and Shadow have enough importance and popularity to make sense as racers.