Nilok
Smash Journeyman
Sorry, I choose to focus on the main 3, Shadow, Knuckles, and Tails as they have the highest chances of being Playable Characters. So I will add a pair of Villains into the mix.
Dr. Ivo "Eggman" Robotnik: has a large fan base, and since he is the original sonic villain, he carries a lot of weight (I made a pun). If he would be playable, I see him using some sort of machine, such as his Walker from Sonic Adventure 2, or a Brawl exclusive robot that makes use of Robotnik's concepts. Because of Robotnik's status, he would probubly be placed between Shadow and Knuckles but will most likely be a Boss for the SSE.
Mephiles the Dark: For being in a lack luster game, Mephiles has a decent sized fan base thanks to the fact people have posted the Sonic 06 cut scenes, and the detail put into his characters such as voice work, movement and personality. If Mephiles was in Brawl, he would probubly be a slower characters, maybe as slow as link, but he would has an array of ranged moves and use some warping attacks. Mephiles places between Metal Sonic/Neo Metal Sonic (Lord Metal) and Tails, he has a good fan base and character design and is a villain, however he is from a new game and a bad one at that.
Dr. Ivo "Eggman" Robotnik: has a large fan base, and since he is the original sonic villain, he carries a lot of weight (I made a pun). If he would be playable, I see him using some sort of machine, such as his Walker from Sonic Adventure 2, or a Brawl exclusive robot that makes use of Robotnik's concepts. Because of Robotnik's status, he would probubly be placed between Shadow and Knuckles but will most likely be a Boss for the SSE.
Mephiles the Dark: For being in a lack luster game, Mephiles has a decent sized fan base thanks to the fact people have posted the Sonic 06 cut scenes, and the detail put into his characters such as voice work, movement and personality. If Mephiles was in Brawl, he would probubly be a slower characters, maybe as slow as link, but he would has an array of ranged moves and use some warping attacks. Mephiles places between Metal Sonic/Neo Metal Sonic (Lord Metal) and Tails, he has a good fan base and character design and is a villain, however he is from a new game and a bad one at that.