I liked the idea of their final happy ending being an afterlife reunion, with Rumplestilskin sacrificing himself after Belle had died after they'd lived a long life together. It was the only idea which fit and resolved the issue of his immortality while also working with the times the Darkness had been defeated previously. Alternatively, they could have had them move to live in the World Without Magic and live out a full life there, but I think this worked better.

I'd have liked to see more of their adventures travelling all the worlds as realms, as Belle had always dreamed of doing. I think that would fit her better than settling in some isolated little house. But I understand that it was easier to film it that way. I also think the couple would have preferred to live their lives alongside their friends and family, but again real-life filming/story-telling concerns prevented that. They needed to have a post-Belle's-death Rumplestilskin around at the same time as the other characters who remained for season 7.