Delta and Sigma were scapes meant for us to challenge others. The "finalist" round of this tournement would be finalists from multiple worlds, not just one specific world. Because of that, I stand by the fact that it will be made up of Super Bosses from the entire series, including Ruby Weapon, Penance and Absolute Virtue, followed by Omega. They could take the lazy route and throw in several Dissidia resources and have us fight Sephiroth or Kuja or whatever, but that's tacky. Especially Sephiroth--since we literally just fought a winged god that uses half of his moves.