I’ve also been thinking about the Reydream. It would be ideal to show it as an actual dream somewhere, but I don’t think it would work so late in the movie. Maybe just toning down what is there even more, so that she sees only a really vague outline of the island, would work and be less jarring for a first-time audience. They might interpret it as more of a mirage than anything on the first viewing.
My idea for the interrogation is actually one of the things I’m most excited to work on, when I finally get the chance. In particular, I’d like to use the as-of-now unused images of the Starkiller beam traveling past the destroyer, since that with the voiceover of Kylo saying ‘I’ll finish what you started’ would strongly connect him in favor of the Starkiller and provide an interesting point of departure from Vader ANH. I’ve discussed the full sequence previously in the thread, but suffice it to say that I intend to make this scene much more intense.
I don’t actually have strong feelings on Phasma one way or another. It’s a shame that she’s such a non-character, but on the plus side she seems to be Finn’s primary human point of grievance with the First Order, so taking her out of the last act might negatively impact Finn’s story.

And on that note, please do share your thoughts on Finn! He’s my favorite character from TFA, and recently I imagined the movie with him as the main character. There’s a good argument that Finn and Rey are both equally important main characters in this movie.