I was talking with LoD about this before. I think that the character of Vergil is heavily influenced by Darth Vader/ Anakin Skywalker. This in the whole, young man who is skilled with a sword, becomes obsessed with power, succumbs to evil and becomes encased in armour which becomes the embodiment of evil in turn. He fights a relative, loses to him and is not heard from again. On top of this Nelo's sword and spirit swords are all blue which is the colour of Anakin's lightsaber. Other similarities are that both of their armours are complete with bad-ass capes and both try to fight the power that's influencing their evil behaviour before the end.
Just a thought.