I thought it might be a cool idea to make an idea for Sonic Adventure 3, one of the most requested "3" games out there, and certainly the most highly requested Sonic game. The catcher, though, was that I didn't have much of an idea of what an original story would be. However, what spurred me on to make this idea was that I realized that Sonic '06, the most widely disliked game in the series, was probably intended to act as Sonic Adventure 3, but it took the form of a series reboot.
So, really what this idea would be is a remake of Sonic '06, but technically fixed and put in a more modern style. However, its gameplay would be more like the Sonic Adventure games in antiquity, so you won't be able to hold down the boost and crash through the level.