@M3lon If housing could be isolated with no impact on other parts of the economy, this might be workable, but it's inherently linked with the finance sector, with employment, with pensions, with investment etc. The UK has opted for a strategy where we engage in Keynesian strategies to avoid subprime investments (including mortgages) from resulting in a fiscal cliff. We, along with other major world economies, have determined that a restructuring of the economy would be disastrous, and that means that we cannot and will not allow banks to go bankrupt. We bought into this policy completely under the premiership of Gordon Brown, which makes it even more difficult to now go against that, it's unlikely we'd be able to - or want to. It's difficult to project the damage this would have on people: if we think social inequality is overwhelming now, imagine a complete destabilisation of the currencies of the UK, EU, US and China. We'd likely have to go back to the gold standard, and it would take generations to recover from. And all of this for a situation that wouldn't allow people to buy houses anyway? Because there would be a huge credit crunch, refusals to sell from banks/owners regardless of defaults, economic uncertainty, wage deflation -- it would mean that house prices wouldn't actually reduce in real terms.
And on the timing of this: if you introduce a quota that you reduce over the course of ten years, house prices wouldn't fall gradually. The very existence of a quota with this reduction being credible (this is the entire point of a quota) would almost immediately be reflected in the financial markets.
I'm not defending banks at all though. The solution here, I believe, is the introduction of proper punishments for bankers who engage in subprime investment strategies - including mortgages, properly. The potential of introducing 'rent control' on the growth of house valuations in line with inflation may be an option, however that would be a major turn away from the economic system we have subscribed to and would be a turn toward a very far left socialism.