Holy! Guess Metal is the next playable character.
I sent that mail to gamefam asking them to spice it up with other ways to unlock characters than just collecting stuff. Not long afterwards the Treasure Hunting Knuckles event started.
If I could lead the Metal Sonic update, I would have Metal Sonic unlocked after finishing a series of races with Metal Sonic. Special courses can be plotted around Chemical Plant Zone and, like certain Town Missions from Sonic '06, the player must race Metal Sonic through a series of hoops and beat them in a race. All the while the speed of Metal Sonic is the same as the players, with a minimum cap requirement to compete against Metal Sonic.
What's likely gonna happen though is we'll probably have to collect power crystals, data cards or some shit like that than anything engaging.