Are lifeboat ethics really about sustainability?

One more thought from the conference, about so-called "lifeboat ethics" - I think its a flawed, or at least incomplete, analogy. A lifeboat is only going to be able to hold so much weight before it sinks, and this part does make sense when considering the Earth's limited capacity to produce nutrients for its inhabitants (also called carrying capacity). But the question is: how is that weight distributed among the people in the lifeboat? In deciding who gets on the lifeboat, is one of the first qualifying factors how much weight someone is bringing, how much space someone takes up and how that relates to saving the most people?

If the goal is really to preserve the human race for the future in an ecological crisis period, your criteria for who gets to live are the following: people who have the most sustainable relationship with each other and their ecology; people who can lead and teach sustainable living for future generations; and getting the maximum number of those people to continue into the future. Note that technological advancement and wealth are not on this list, along with many other highly prized qualities of modern society ... and that the first two criteria tend to eliminate most people in the world's power centers. Would these leaders be giving such consideration to the lifeboat model if they knew they wouldn't get to go? Is this model truly about what will help humanity to survive the best way into the centuries ahead, or is it really about maintaining existing power structures and eliminating society's "undesirables"?