The problem with glossiness mapping is, that it is VERY dependent on concrete situation, so what seems fine in one scenario might be quite off in another. Also changing it would affect existing scenes, so I prefer not to mess with it, unless its really clear, that it is off.
Anisotropy is (should be ;)) relative to world coordinates
Displacement should never make holes, if the base geometry is sane and it has single smoothing group. Try using single smoothing group for your model, or at least the displaced parts
Why do you want reflection dim distance? That is one fake I do not want to implement, because I see no use for it. The overall attitude is that you should be able to get by in Corona with minimum fakes, because the renderer should handle most situation without them.
Other things are doable and will eventually get implemented. Unfortunately, I dont have time for it right now (1-2weeks)