Earlier quoted context omitted.
"If a government were to do that for everyone it seems pretty obvious that society will be better off - people will spend their time working on things to improve everyone's life rather than worrying about how to afford their rent." Looking at populations of people who have gone from being very poor to being very rich overnight does not support that statement. Most of the time the money is more of a curse than anythin…
The most galling implicit premise of all is that every proposal for basic income I've ever seen accepts that BI isn't practically feasible with open borders, and therefore nothing changes at all for the class of people who work the longest hours in the worst conditions (indeed their wage slavery becomes even more essential to ensuring future riders of the purple wage can still buy consumer goods) An argument for impl…
They may have done it mainly for the benefit of their own heirs and successors, but now that it's done, it's done. All those improvements multiply, and Brits get more because it takes less individual effort to produce the same amount in the heavily-improved UK than in a country where improvements are more easily destroyed or converted. So anyone willing to obey British law, participate in the British economy (accept and spend pounds), respect British infrastructure, and assimilate into British culture should get more than the rest of the world, because those are the practices that allow Britain to be more productive than the world median.
A hedgerow along a country lane does not grow that way naturally. It takes an effort to force it. But once established, it just needs a regular trim and an occasional re-laying to keep the livestock out of the road. You just don't need to pull a new barbed wire fence in front of a blackthorn hedge, so why would anyone complain that no one is doing it?
The resources of the country are preferentially distributed to its own citizens because one country lacks the sovereign authority to force any other country to change its culture and institutions to be more productive. If those other countries wanted to be as prosperous as Britain, they could fork the British system, or selectively merge changes from it into their own repositories. See also: USA, Canada, Australia, New Zealand.
So those people aren't exactly thoughtlessly doing nothing. They are being British, as hard as they possibly can. And that allows the UK to have nice things like the NHS. In contrast, Americans, in being as American as possible, can only manage a hybrid public-private healthcare monstrosity that no one can examine too closely or for too long, because most of our psychiatric hospitals are cleverly disguised as prisons.
In light of that, there's really only one essential element that needs to go along with open borders. Assimilate the immigrants.