Custom material shader concept for BGE

concept.glsl

// Generated code. Not visible.
uniform struct TextureSlot {
  vec2 offset;
  vec2 scale;
  float intensity;
  float lodBias;
  bool isNormalMap;
  int blendMode; // Mix, Add, Subtract, Overlay, ...
  int type; // Reflection, Refraction, Normal, UV, Generated.... This will determine which UV mapping algorithm to use.
  /// and much more...
} vTextureSlots[8]; // Properties for each texture
uniform sampler2D vTextures[8]; // 8 is the max textures on my hardware.
// End of generated code

in vec3 vPosition;
in vec3 vNormal;
in vec2 vTexCoords[8];
in vec4 vColor;
void main() {
  vec4 col = texture2D(vTextures[0], vTexCoords[0]);
  gl_FragColor = col * vColor;
}