After playing around with materials attempting to create characters with Shadow Mario Textures, I ended up modifying it enough and feel like this actually came out pretty nice.
Most of you are probably aware of the issues with putting Yoshi on an extra slot (effects that stay forever when you drop shield, etc), but regardless, it's TexID fixed to be put wherever.
It may appear that textures are corrupted upon zooming in, but these artifacts showed even with default textures and just material edits, I've moved material settings around and can't seem to get rid of them while preserving the transparent effect, they are generally unnoticeable in game with the most noticable appearance probably being the results screen.
Includes all UI features as usual and edited egg files.
I'd recommended putting it on c07 (white shoes) if you don't like the purple dair efffects (I looked into changing them but they only seemed to change half of the "swipes," the center one still remain the original slots color even after editing and/or replacing all the files in data\fighter\yoshi\effect\yoshi\model\EffYoshiAirTrace03 with ones from another slot, so they must be kept elsewhere.
Anyways, enjoy! (Also if it wasn't obvious, it's not always super easy to see this skin, therefore I wouldn't recommend adding it to builds used in any kind of competitive scenarios...you might get Johns).