It will work but if Bitcoin crashed instead, people ganna default the loans....
wrong. bitcoin always rises from the ashes and you are not possibly that stupid to take a loan for short term. With bitcoin long term is your friend. For unexpected crashes you will need to have the plan B (maybe read my hypothesis again).
By your logic you can take 50.000$ loan, buy 100 Bitcoins and you can make 500.000$ in a shot amount of time? Do you really think bitcoin will be worth 5000$ and if you think why don't you risk it and buy? Don't go to bank, talk to family members, sell house, car get 100.000$ and invest if you are sure that scenario is possible...