There was a couple of those from v2.1. Garrulous64 reviewed one of those mods twice, (one just a sample, then a stream) which was just a retexture of the vanilla levels with redrawn textures, then repainted in the style of Encore Mode. That was made by the same guy who made this.
Another popular one still palette swapped the levels, but instead of redrawing the textures, there are some changes in level layout across the entire vanilla campaign. It was made by the same person who later made Team Kinetic.
Speaking of the latter Encore Mode mod, that one had character swapping mapped to Toss Flag. Why isn't that the case here? Instead, we got Custom3 for character swapping. Keep in mind that some characters (Modern Sonic and Adventure Sonic in particular) have some of their actions mapped to that, and that's just not convenient. Maybe it is to PC players where their controls are customizable, but mobile players aren't so lucky. We ain't got custom mappings for controls.