Dark Paladin Danny
Kefka Cultist
First off, I think they only put in Gogo so they could have nine main character in the game as well as part of the ending (if you get him) where they need his mimic skills to get out of the tower, second I don't think Gogo is Shadows friend, or Shadow (if you can get him back) would most likely know it's him.
As far as I know, they was going to add that to the game, but they ran out of time so they left her dead.
Nine? Theres Fourteen main characters, you need twelve just in the last dungeon
Also Aeris wasn't going to be revived, just killed off much later
Also, Gogo is Gogo, the mime in FFV who flung himself into the "X-Zone" spell, and of course you meet him in the "Zone" Eater