This stuff actually has been widely experimented with (ie) however it is really not used outside of the technical community. Your best chance to get started with this stuff is going to Minecraft technical/command forums or discords and asking about core shaders.
If you need help setting it up and editing the textures, I recommend you follow this, and edit the textures in your preferred image editing software (like ms paint[probably shouldn't use], or any software that you can edit images with)
I searched the texture assets for passive mobs, I couldn't find any textures for specifically the baby mobs. You can try to create a custom model and put it on an armor stand's head riding the baby mob, but I have not tried that.
