None of these characters are original, so you could probably steal them.
Sega finally revealed the mystery character in Sonic Forces. No, it's not Bubsy the Bobcat -- it's you! Sonic Forces is going to include a character creator so you can include your original character (do not steal) in the game. Honestly, it's a little surprising Sega hasn't done this before. Few franchises have more 'OCs' created for them with a little recoloring and some added accessories than Sonic the Hedgehog.
Maybe Sega's been taking notes from Dragonball Xenoverse?