This is more a discussion for the TFA thread where it’s been done to death, so I’ll add that Rey finding Luke’s lightsaber - in the context of TFA - is a convenience on multiple levels.
In the OT, when someone lost a lightsaber in a duel, especially over a bottomless pit, that’s fairly clear cinematic language for ‘gone for good’. The fact that Luke’s saber was found is already a convenience, and that Rey finds it during her first stop off-world is yet another. If the scene was powerful on a thematic level then I’d be more likely to give these conveniences a pass, but it isn’t, and they could easily have had some other artifact or situation to give her the Force vision and then later had her steal the saber from Kylo, who has already been established as being an obsessive collector of Vader artifacts.
Speaking of sabers on a thematic level, the duels in ESB and ROTJ mirror each other. The loss of Anakin’s old saber could be interpreted as a metaphor for the loss of Luke’s idea that his father was a pure and uncorrupted Jedi. Similarly the loss of Vader’s saber could be interpreted as the loss of his identity as Vader. Finding one of the two sabers later on implies an extension of the metaphor, and confuses it. Is Luke’s saber still a symbol of an uncorrupted Jedi? How does this play considering that Rey is very clearly angry and using the Dark Side during her fight with Kylo? Is the saber to Luke a hopeful symbol of idealism, or a painful reminder of his false belief and failure? The film could have given us something to guide our interpretation, but it’s left too ambiguous. Rey is confused and terrified at the vision of the saber, so she doesn’t help us out with interpretations. The clearest interpretation is that it is a sword-in-the-stone moment. Presumably Rey is another divine chosen one, or the daughter of Luke. But if she is the daughter of Luke, that raises even more questions!
I guess my biggest problem with all of this is that I don’t think that JJ had any of these other thematic ideas in mind when he made the scene. I think it’s supposed to be confusing and defy interpretation - not through subtlety or inter-textual clues, but through withholding of essential plot information. And that irritates me.