Load texture at full resolution when using quality settings

I'm struggling with very strange problem. I'm using quality settings to reduce memory usage on mobile platforms with half textures. But there are some sprites, which I need to load at full resolution with mip maps. I'm using www class.

 var txt = new Texture2D(1, 1, TextureFormat.ARGB32, true);
 
 //this will turn off readable texture 
 txt.Apply(true, false);
 www.LoadImageIntoTexture(txt);
 var pixels = www.texture.GetPixels(0);
 
 //HACK ??? I thought, this could work
 txt.SetPixels(pixels, 0);
 //not updating mipmaps, but first mip map level is still half
 txt.Apply(false,true);
 
 www.Dispose();

This code will load texture successfully,but unity will throw away first level of mipmaps from texture. I've tried also second approach, where I am not using method LoadImageIntoTexture, and setting pixels via SetPixels direcly. I suppose, that method texture.Apply is looking to quality settings and if using half textures, than first level of mipmaps is ignored.

Does anybody know some workaround to this ?