apparently this doesn't work properly in 1.21.1 because all i tested was the model. my b. gonna take more work than expected. should be better next release.
licenses this project includes: https://gitlab.com/cable-mc/cobblemon-assets/-/blob/master/blockbench/pokemon/gen1/0025_pikachu/LICENSE vanilla model's license, /datapacks/poke-costume (MIT) the hat
SK4N's eeveelutions reimagined required for eevee in v5 (1.7+ will not require it, but still recommended)
TODO (1.7): 0. make it actually work in 1.21.1 1/2/3. pikachu revamp/cosmetic item integration/pokedex 4. actually shading the pixels to look good
i activated the pikachu form using a datapack, then added an edit of RedRibbonz pikachu model for this.