The Enigmatic Man

This character is first introduced in a scene only in Final Mix.
This unknown is the only one you actually encounter during the game. It is also unclear which one he is in deep dive. You physically cannot see any of his face and he wears the same exact raincoat that they all do.

In the scene, he makes two very important references. One, being to Sora when he told him "He looks just like you." This is a clear reference to the conversation between the unknown on the beach. This is also why the assumption is made that Sora looks just like the glowing eyed unknown..
The other important bit of information he reveals is that "He is a mere shell". This would lead us to believe that is a "non-existent" one. This is the origin of the theory that all the unknowns are non-existent. If he is just a shell then who's shell is he? Can we assume that it is not Sora just because he said "He looks just like you" and not "I look just like you"? His identity still remains a mystery.
Which unknown from Deep Dive is this enigmatic man? We don't have that much info to go on besides comparing his cg rendered character design to pictures of the unknowns from the video. While not a completely reliable method because in-game character models differ from the

models it's as good a method as any at this point.
The boots are Similar to those of the glowing eyed unknown. But does this prove anything? Of course not, as if anything on this site proved anything. However, this does tell us that the enigmatic man is more likely to be the glowing eyed unknown than the dual wielding one.
However, because of the nature of the similar comments that the sitting unknown made to Sora and to the glowing eyed unknown, I would say that another educated guess is that the enigmatic man is this speaker.