I think it would be cool if the final boss was a friendly rival of yours at the beginning, but at the ending of the tutorial level he turns against you and you have a duel. If you lose to him, he will still be a difficult final boss. However if you defeat him now, his hate for you will become so strong he will train to become way more difficult as the final boss. The duel in the tutorial level could also affect what kind of techniques he has in the final battle.
Also in the final fight, you won't be able to recognize him because he has changed so much. You will realize during the final cutscene that it was your former friend.
*edit* Oh and he could even be some ancient character from the lore, such as Lloyd or Arstor. Because the directors said the main theme of the game will be "time" and different eras. I think they might have hinted that the age you live in changes throughout the game. This way the final boss battle could be a thousand years later from the tutorial.
Also in the final fight, you won't be able to recognize him because he has changed so much. You will realize during the final cutscene that it was your former friend.
*edit* Oh and he could even be some ancient character from the lore, such as Lloyd or Arstor. Because the directors said the main theme of the game will be "time" and different eras. I think they might have hinted that the age you live in changes throughout the game. This way the final boss battle could be a thousand years later from the tutorial.