In the TLJ Spoiler thread, Mithrandir made some great points about how TFA set things up that really limited how to handle certain matters like, foremost for many, the characterization of Luke. Why was Luke on that island? To forsake the world? If so, why? What reason would feel compelling and within character? If there was a deep and meaningful reason to be on the island, how does that outweigh all else?
The dark side temptation is one possible solution I didn’t consider. We would still want to know why and how he is being tempted. We might find that Snoke is so powerful he is driving Luke to madness, having planted a seed of doubt in his mind, and not that Luke is actually being threatened to be consumed by hatred and anger within himself.
In my own effort to respond to the challenge of Mithrandir’s argument, I have come up with another possibility. I haven’t offered a complete outline of the film as you have but rather focused on setting up Luke’s part in this story. The story would start much like actual TLJ, but with more Resistance ships and one fewer joke…