What I like about the third movie is you get to see a side of Carlisle you haven't seen before. You actually get to see what his vampire capabilities are because there's some great battle sequences. It's my favorite book. Carlisle is holding on to that humanity. He doesn't want to be a vampire.
Once you come up with a premise, you have to work out how it all happened. It's a bit like coming up with a spectacular roof design first. Before you can get it up there, you need to build a solid foundation and supporting structure.