I totally think there should be a side story for Sparda. It should tell how he met D and V's mom. Also his weapons should be the Rebellion, Yamato, and Sparda/Force Edge. The final boss could be Mundus. Also Berial and Phantom and Beowulf becuase Beowulf met Sparda that is why he is blind and Phantom met him too. I think since Berial is Mundus' succesor Sparda could face off against him first.
Death comes swiftly to those who fear