It is possible to actually go through Aron's quest without actually getting Laya (Though you still need all 5 legendary weapons to complete the game, one of which Laya has). In order to do so, you have to give Laya's Bow to either Wren or Mieu during Nial's quest. When Aron's quest begins, Laya's Bow will still be with them, meaning that you don't have to find Laya to get that item.

This does raise the challenge value of the final part of the game a little bit.