Sauron's Super Army?

[Mornorngûr]

Yeah I guess you are right, Iziladun. Sauron probably wouldnt have recovered any of 'The 7' by this time, and he would not have been able to to determine their effects on the wearers.

More importantly though, Sauron might not have wanted the masses in Númenor seeing what the end product of the wraith-process really entailed. It might have frightened them enough to have turned them off their path in which they strove for immortality. My thought of that is that the state of the Nazgûl was actually what immortality was for a mortal. They could not get new life, only a lengthening of what they had already, and seeing that displayed openly in the figure of their king might have led to some serious soul-searching which could have derailed Sauron's plans.

I suppose this was indeed the only kind of immortality to be had by a mortal and like you say seeing it would have terrified them. 'The Faithful' did not agree with how Ar-Pharazon was ruling (under Sauron) and still more Numenorians would have been horrified if their king became a Wraith, and would turn away from him.