This is an important point, because interest rates would exactly make up for the undesirability of the inflationary currency; i.e. the inflation risk would just

This is an important point, because interest rates would exactly make up for the undesirability of the inflationary currency; i.e. the inflation risk would just be "baked into" a lower interest rate for the dollar-denominated loan. Unless you had a substantially different inflation risk tolerance than society as a whole, you'd be neutral about what currency to make the loan in. Same goes for the borrower and deflation risk. Edit: I guess if the deflation risk tolerance for the borrower and the inflation risk tolerance for the bank are asymmetrical, then you would just end up with being able to loan one or the other. I suspect, per Slurry's point, that it's BTC that loses here.