Mapping with vanilla textures

Hello,

Just a little feature request: could you add the ability to map vanilla textures on 3D models (from json files). It would allow users to have the textures of their own ressource pack on the block or when updating the mod from 1.12.2 to 1.14.4 for example refresh textures automatically. Finally it would decrease the file size (because we don't have to duplicate the vanilla textures in it).