With respect to the original post, note that DL has just acquired 49% of Virgin (from Singapore) and is commencing code sharing, in preparation for a full blown joint venture in early 2014. I presume that both airlines would ideally want to move Virgin into Terminal A, or worst case into B1-B3. If so, that would require some reconfiguration to your original plan. Maybe Virgin and Spirit swap locations somehow? The key question is how many gates each airline is going to want.