That's classic fractional reserve banking and it works with dollars, bitcoins, gold, or seashells.
Agreed - except perhaps with the caveat that when it all goes tits up (frb under BTC) and 100,000 x Jo Bloggs' default on their loans, the Govt. won't be able to prop up the banks that made those loans using QE. I guess taxation would still be an option - but would this be enough in the absence of QE ? I dunno.
IOW - wreckless lending wouldn't be nearly so attractive when the safety net has been taken away.