Yes narratively bound is my new favorite word. So a lot of sidemissions are usually just throw away meaningless fetch quests that add very little to the emerging story and honestly in many cases just take you out of the experience when you choose to do one. I have a solution to this problem. Imagine you hit a wall in the main storyline. You are suppose to hunt someone or something but you don't know what or who. What sidemissions can do is to give you hints in what direction to go in. Eg a sidemission reveals that the person you are looking for likes to party? Next sidemission tells you the man you are looking for has green hair and so on. Now you can use those clues to narrow down your search or keep doing sidemissions until you are certain where to go exactly. Now i used a very primitive example here but this is a good way to weave the sidemissions in with the overall story.