Price and Non-price Rationing

Civitas, a reliably dusty old right-wing authoritarian think-tank have, somewhat to my surprise, published this:
Overseas investment in London homes must be curbed to help reduce rampant house price inflation and ease the housing shortage, a new Civitas report says.
The UK property market is being used as an investment vehicle by the global super-rich while hundreds of thousands of younger residents are being priced out of the market and rents are eating into more and more of people's salaries.
A Civitas paper published today calls for new restrictions on overseas buyers seeking to use London's limited housing stock purely for investment purposes.
The think tank says that non-residents of the UK should only be allowed to purchase a property here if that investment will add to the number of homes.
The idea reflects the system in place in Australia, where all non-residents wishing to purchase property must apply to that country's Foreign Investment Review Board (FIRB).
While I agree with the general sentiment, this sort of non-price rationing never works of course.
People always find ways round it - as a matter of fact, "the global super-rich" have been primarily buying new-build homes - as the full report says* (and leaving them standing empty). And how on earth would you prove that somebody bought something "purely for investment purposes"? How many days a year would somebody have to live in a home to get round the rules?
And isn't the whole basis for Home-Owner-Ism that people buy housing, whether to live in or rent out, for "investment purposes"? How come that's a bad thing all of a sudden?
Price rationing would work far better - can anybody think of a way of getting those of "the global super-rich" who own land and buildings in London to compensate "hundreds of thousands of younger residents" via the tax system?
And if we agree with the general principle, why shouldn't the same apply to wealthy Londoners snapping up second homes and holiday homes in the South West or on the South Coast?
* "The new-build market in central London is dominated by interest from overseas, meaning that even relatively well-paid young people wanting to buy their own home now struggle to do so...
There are even warnings that, as well as driving up prices for domestic buyers, the nature of investments from overseas is distorting house-building priorities, with developers disproportionately attracted to high-value developments while ignoring the undersupply at lower levels of the market...
Unfortunately, not only is the government’s default setting to quietly encourage house price growth, it is also to do nothing that would impede overseas investment – without regard to whether it is having a deleterious effect."