textureCombine.cs

Texture2D[] layers;

Texture2D compiledTexture = new Texture2D(layers[0].width, layers[0].height);

foreach(Texture2D layer in layers){
	
	Color[] baseColors  = compiledTexture.GetPixels();
	Color[] layerColors = layer.GetPixels();
	
	for(int p = 0; p < baseColors.Length; p++){
		
		Color resultColor = baseColors[p];
		
		resultColor.r = baseColors[p].r * (1.0f - layerColors[p].a) + layerColors[p].r * layerColors[p].a;
		resultColor.g = baseColors[p].g * (1.0f - layerColors[p].a) + layerColors[p].g * layerColors[p].a;
		resultColor.b = baseColors[p].b * (1.0f - layerColors[p].a) + layerColors[p].b * layerColors[p].a;
		
		baseColors[p] = resultColor;
		
	}
	
	compiledTexture.SetPixels(baseColors);
	compiledTexture.Apply();
	
}

This is amazing & exactly what I've been looking for!