Highly unlikely. Barthandelus has been in control of Cocoon at least since the War of Transgression (as he is mentioned by name as taking Fang and Vanille to Cocoon after Ragnarok failed). He may have taken various guises over time, but the Primarch has likely always been Barthandelus. He's way too much of a control freak to have let humans rule themselves for hundreds, if not thousands, of years.

It is possible that there was someone named Dysley, who was working his way towards becoming Primarch, but Barthandelus would have killed him and assumed his identity before he stepped into the role.