In the game there is a line of dialogue with Arngeir after defeating Alduin in Sovngarde asking if Alduin is really dead and I saw this line the other day again and it occurred to me that a Quest mod could be made about this.
This can be linked to the fact that the Dragonborn isn't fully trained in the way of the voice. In the vanilla questline when you ask Arngeir if you can be trained more he says it isn't time yet or something like that (I can't quite remember), hinting that there is further training involved. Maybe Alduin can only be properly vanquished by a fully trained Dragonborn.
Further training could possibly include shout crafting, meditating on multiple shouts to buff more than 1 shout,and having a power to shout without cooldown for a period of time (Or possibly the ability to shout without cooldown all the time but with a debuff for abusing this like 'sore throat: You cannot shout for 48 hours')
Edited by Colinvolt, 28 February 2015 - 11:08 AM.