Your brother-in-law made some disastrously bad financial choices, apparently.
Yes - him and half a million other UK households
still in negative equity - not to mention those who sold at a loss. But to suggest that it was a choice on his/their part is to misunderstand the
debt based economy.

Kind of reminds me of The Great Depression/the Installment Plan. History repeating. The punctual always have to pay the price for the tardy - or, to put it another way, the little guy always picks up the bill.
Banks could issue promissory notes backed by bitcoin ie. credit - but in the event of a default there would be none of the traditional (Friedman monetarist) solutions. It would help to rewrite the question - and so the answer- in large ,clear, legible and bold text.
BTC