If Miku can be Chip for a Sonic Unleashed Recompiled mod, then I want Slug and the King Amoeba from Goonya Monster as Sonic and the Werehog respectively (which means extracting the models from Goonya Monster itself, something I obviously can't do for a multitude of reasons (and the King Amoeba is the Werehog because I believe it's actually a stretchy thang))
(If you're unaware of what Sonic Unleashed Recompiled is, it's an unofficial PC port of the original game)
Also, I thought of a parallel AU for @GaiaKoraidon's Heart of a God, Soul of a Warrior using the Light Gaia Sonic fusion she designed called Body of Light, Spirit of Earth. Here, Dark Gaia suddenly gets the upper hand in the final battle, and Chip, with his control over the Gaia Colossus weakening, forces Sonic, in Super Brighthog form (he gets depowered into base Brighthog form shortly before this by an attack by Dark Gaia), to fuse with him so they can win once and for all.
In the three years since he left for Eggman Land, the hedgehog has since been declared missing, presumed dead. Sonic's friends hold up hope that he's alive and well somewhere, which he is, within the planet, but he learns that he can come to the surface with the Light Gaia spawn, and so he takes that chance.
That's all I've really got so far