But bear in mind, Janes know the 748 inside out and back to front, have in house engineering, a bloody big stock of spares, 748 type rated crew and bucket loads of experience.
As you say fuel is fuel, but its not only fuel you have to look at here. Surely its more cost effective, especially with a sart up, to work with what you have and reduce costs in other areas as above then why not stick with it, they do there job well for the environment they operate in.