Chekhov’s gun is a literary tool that is used to cut superfluous dialog, scenes, and action in a story.
“Remove everything that has no relevance to the story. If you say in the first chapter that there is a rifle hanging on the wall, in the second or third chapter it absolutely must go off. If it’s not going to be fired, it shouldn’t be hanging there- Anton Chekhov
We know that Rian Johnson had some input on The Force Awakens to better serve the rest of the story that he would be telling in Episode VIII(writer & Director) and Episode IX(writer).
Rian has asked for a couple of things here and there that he needs for his story. He is an incredibly accomplished filmmaker and an incredibly strong writer. So the story he told took what we were doing and went in the direction that he felt was best but that is very much in line with what we were thinking as well. But you’re right—that will be his movie; he’s going to do it in the way he sees fit. He’s neither asking for nor does he need me to oversee the process.- JJ Abrams
The question is then what parts did he have added or cut to better serve what he wanted to tell. In other words what “rifle(s)” did Rian want for his movies? We’re going to explore a few options of small scenes/phrases that did not have a resolution in TFA and Rian could possibly be using to further his story.
Rey’s Parents/abandonment: This one is pretty obvious as an unanswered question that the audience needs/wants answered. We’ve discussed both of these a few times here, here and here. I think its fair to assume that this will be answered one way or another and I suspect that this is one secret Rian wanted to reveal himself. At one point Daisy said we would know about her parentage at the end of TFA. Obviously we don’t but she may know already because JJ originally had that written in the script. Depending on who her parents are this could be anything from a pea gun to Death Star in terms of importance. I tend to lean towards death star size but that’s just my opinion.
The Knights of Ren: They are only mention once in TFA as a through away line from Snoke to Kylo Ren. We saw only one shot of them in TFA and they were not named as such during the shot. They were confirmed as the Knights of Ren by other official media(books interviews etc). Obviously they play a part in the history of either the Skywalker lightsaber or Rey herself since their one shot was during Rey’s “forceback”. The question is now what role do they play from now on? Do they act as Jedi did during the Clone wars commanding the armies on field of battle? Do they have one mission as a group to hunt down and destroy Luke and Rey? If Kylo needs more training and is their master are they even force sensitive?
Snoke’s history: How many questions can we answer by knowing more about Snoke? How does Leia know him? How did he meet Kylo? How did he become scarred? Did he found the Knights of Ren? How did he assume control over the former Imperial forces? He is left as mysterious as Vader was in A New Hope. His history and his intentions are have not yet truly been revealed and they likely will have a huge impact on how the story plays out
Luke Skywalker: Why was he hiding instead of being proactive? Has he become the Jedi his father never was? Where was he when his students were killed? There are many things about his past that will put focus onto where the films are going. His abilities will also determine how the trilogy plays out. If he is as powerful as his father once was there should be little that could pose a threat to him, if he has not grown in power and ability since RotJ then him hiding suddenly makes more sense.
The Republic: Mentioned only twice, most importantly about their fleet being lost, the actions of the Republic will determine whether or not the Resistance has a shot against the First Order. The member planets that make up the Republic can make the coming war an even battle or allow the First Order to have the upper hand.