Ever heard of Sonic Freedom? That game has the exact request you have. It takes the Junio artstyle from CD Cutscenes and OVA, and takes it into the completely hand drawn 2D world.
(Fun fact: The same main move you have in the Junio Sonic mod IS from Sonic Freedom)
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Might as well drop my cents here. I would imagine a game where many variations of Sonic team up to stop Mecha Sonic Mk.II across the universe. You can think of the Spider-Verse movies and see what i mean here. These come from:
- Official Game Appearances (Junio, Classic, Adventure and Modern)
- Archie/IDW Comics
- Cartoons, Movie and TV
- Misc. Media and Fanon
You only start with Adventure Sonic at first, but as you progress through the story, you meet and recruit other fellow Sonics like Darkspine Sonic, Sonic-Zilla and others. The gameplay would be like the classics, but has the gimmick used from Encore Mode where you switch characters at any time you can without cooldown.