I love the stylized look of the per-face lighting - a couple of questions and suggestions:
-while the ultimate goal would be per-pixel lighting, please do keep this mode available in the future, for its stylized look - same, if you manage to get per-vertex lighting going (Gouraud-ish?)
-are you working on/considering decoupling texture size from the C3 spritesheet size? This limitation kind of goes against using glb as an all-encompassing format (mesh+texture) - as you still need to take an outside parameter (C3 spritesheet size) into account...