> Assuming the interest rates are the same, I'd agree. Would they be?

I doubt they'd be the same in either nominal or real terms. But that's a side issue.

You could already do what you're talking about with gold. A bank could offer gold savings accounts that pay interest on gold loans. They don't do it. Borrowers are deflation-averse and no one wants to deal with the exchange rate fluctuations.

BTC has some legit uses (like buying unjustly banned consciousness-expanding products over the internets) but the built-in deflationary death spiral in its design pretty much ensures that it will never be a serious full-spectrum parallel currency, much less a replacement for the dollar and euro.