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.
Escapipe Glitch
Early in the game, you can activate a glitch which will prevent you from going any further in the game. What you need to do is when you first have control of Rhys, go to the item shop and sell your Boots. Buy an Escapipe and go to the castle and complete the wedding scene. As soon as Rhys is thrown in the dungeon, use the Escapipe. You will arrive back in the castle in front of King Landen. Talk to him and he will say that you cannot go any further in the game because of this trick.