Still, I think if you wanted to include more of a love story in Casino Royale, the better approach would have been to trim some of the action, particularly the Body Worlds and Miami airport sequence.
That would definitely be my preference for furthering the development of the love story between Bond and Vesper. If I were somehow given the ability to make my own version of the film, it would have started (after the title sequence) with Bond already in Montenegro, and the Poker game would commence soon after that. Much of what follows would be more or less what we got in the film, except there would be probably another hour of footage filmed in Venice that would further develop Bond and Vesper's relationship, as well as Gettler's involvement in the storyline.
I would only have just gone ahead and extended the film to about 2 hours and 50 minutes in my original post because I was trying to stick with what EON was going for with the film, which was a film that was way too front-loaded with action. I would much rather, though, completely get rid of the first hour of the film (save for the PTS) and begin the film when Bond and Vesper arrive in Montenegro.