Which non-playable character would you like/have liked to play as in the story mode of Sonic games?

[Shiny Gems]

And I am not talking about multiplayer mode, or spinoffs for that matter; just story mode, in the main platformer Sonic the Hedgehog games.

I am talking about those such as Mephiles the Dark, Infinite from Sonic Forces, Sage from Sonic Frontiers, one of the Deadly Six from Sonic Lost World, Gemerl from Sonic Advance 3, and though this does not include the story mode of spinoff games, this can still include spinoff characters like the Babylon Rogues, an original character from the Storybook series, etc. Heck! We can even include humans from any Sonic game, as well as characters from the canon IDW comic series, too.

Anyway, which character that has not been playable in a Sonic game would you like to play as in a future Sonic game? This can be one off characters, too, as in those that had only one appearance in a Sonic game.