thats his form not his shade . His spirit could wield the ring and cause him to gain immortal form again
__________________ This thing all things devours:
Birds, beasts, trees, flowers;
Gnaws iron, bites steel;
Grinds hard stones to meal;
Slays king ruins town,
And beats high mountain down.
It's reasonable to assume that reacquainting himself with his Ring would allow him to fabricate a new body.
__________________ Recently Produced and Distributed Young but High-Ranking Political Figure of Royal Ancestry within the Modern American Town Affectionately Referred To as Bel-Air.
As a Maia, Sauron can take an shape he wants. So if he wanted to take a form of a Giant Eye, I am guessing, he could. Though, in the books, Sauron has a body indeed. Gollum remembers seeing him. The use of the term Sauron's eye refers more to his gaze being drawn, not some giant eyeball attached to the Barad-dur. The same king of term is used to describe Melkor, but he never lost his physical form until he was cast into the void.