I think it's a great idea since they seems to be taking peoples houses as collateral if I read it properly little tired.
But seems like a good concept never seen anything like this.
I don't see it working out too well. Mortgages use flat-rate returns based on fiat. Assuming nothing changes in your life, you will have more earnings over time than now. On the other hand, BTC fluctuates. It could go up or down, effectively making it impossible to fully repay the loan (i.e., when I loan out 10 BTC, I expect 10 BTC back -- I don't care if it increased in value 50000% or decreased to 1/200 of its value -- what I loaned is my expectation for return).