My additional scenes would be:
1. One more scene on the mountain after the second tent scene, showing them just talking or a scene that shows how much everything is right for them at that moment, something like the campfire embrace, just leaning into each other and talking.
2. Ennis coming home to Alma after BBM. I want to write that scene.
3. The WHOLE motel scene (duh) or the scene at the diner before they leave for the mountains. Lovely. But to be honest, I do think that the motel scene works perfectly as it is.
4. Their last camping trip (they talk they had about their kids, the "that's one of the two things I need right now...", I LOVE that in the book).
And you know what, just more of them together in the whole movie, I think somebody once suggested to just skip all the Cassie scenes, all the Monroe scenes, all the Randall scenes and replace them with Jack and Ennis scenes. That would've worked fine by me!