The term “labor mobility” rather than “people mobility” takes the edge off of the radical counter-”Social Justice” Social Justice that you advocate. It has a conservative (as in right wing libertarian) ring to it, implying that immigrants are solely good for the economy, rather than good for an ethic that seeks to apply the same standards of justice for all.

Invoking Rawls helps, but the constant use of “labor mobility” injures the humanist dimension by saddling it with that which is good for the libertarian economist’s particular obsession.

The problem is numbers — immigrants would swamp and destroy the economies and social orders of the rich countries. And the continuing success of those wealthy countries is critical to the ultimate lifting out of poverty of those in the developing world. And by ultimate, I don’t mean in the sense of ‘in the long run we are all dead’ since Japan, Korea, China and the smaller ‘Asian tigers’ have made stunning progress in periods of time shorter than a generation let alone a human lifespan.

I think industrialized countries could take many more immigrants than they do and that this would be a good thing, but unlimited mobility would be a disaster, I’m afraid.