Fool fits Nobuo just fine :lol Though if we're looking for inner meanings, "the Moon Arcana is associated with creativity, inspiration, dreams, madness, illusions, fear, fantasy, the subconscious and trickery." A good chunk of that fits Nobuo's theme of being a Delusionary Ranger.

Though figuring out a Stand for him... Hm... [Cyclone Effect]?

As for the powers, how about instead of losing our powers but gaining the Stand Powers, we gain the Stand Powers onto of the powers we already have and keep them after the challenge ends. It keeps some continuity to things.