Yup, you're right, I also hate JPig a lot. However, the last puzzle will come from JPM.
KKR has to make more than 7% for her investors, then loaning money for the mortgage definitely is not her business. KKR could be just a bridge.
The cheapest cost of borrowing money is from retailing banks. At the present, bank pays 0.1% for the saving account. The 15 year mortgage is around 3.15% as long as banks maintain enough liquidity.
We need the last puzzle which is the retailing banks. NSM had a very high operational costs. KKR, SoftBank as well as fortress could not reduce the operational costs, bank is the only one can do it.