So you don't what to deal with the simplest case and hope that if you complicate matters, it will somehow help you? Okay, there is 5% deflation (and 5% inflation) already under the way. Nominal interest rate is 0% under deflation, and 5% under inflation.
You cannot have 0% nominal interest rate under 5% deflation, and only 5% interest rate under 5% inflation. Their difference should equal 10%, not 5%.
Otherwise we are in different conditions of real interest, that is, borrowing would be much more expensive in real terms under your deflation conditions than under your inflation conditions. The whole point is that for every percent of inflation, the nominal interest rate will also rise with one percent, and for every percent of deflation, the nominal interest rate will also decrease by one percent.
So if you want to consider 0% interest rate at 5% deflation, you should consider 10% interest rate when there is 5% inflation.
But the case of 5% deflation, 0% interest rate, and 5% inflation and 10% interest rate, I want to do:
a) deflation case:
I borrow $1000 at 0%, I would have sold at $1020 (2% ROI) but because of deflation, I can only sell at $970. $30 LOSS.
b) inflation case:
I borrow $1000 at 10%, I would have sold at $1020, but because of inflation, I can sell at 1070. I have to pay $100 interest. $30 LOSS again.
Why ? Because the real interest rate is 5%, and my ROI is only 2%, so I LOST 3% in both cases.
c) neutral case:
I borrow $1000 at 5% (real rate), I sell at $1020, I have to pay $50 interest: again a loss of $30.