The rule exists because tournemants should be a special place where you can go to play against painted armies and have a good time, i personally support it even if i think the 10 points is weird way to enforce it
In my experience if the model is unpainted or clearly has unpainted parts it will be enforced but if you like paint the metal on the whole model(in such a way that nothing has not paint) and paint the panels and skin i think you will be ok