How would you go about doing this? As an example, if you loaned someone 167 monero to buy a car and expect them to pay you back in 7 years like a bank does you would be requesting 167xmr*6.02% (to counter xmr inflation) for a total of 177.053xmr. 177.053xmr/84 (months in 7 years) would be 2.107xmr a month. At the moment that is fine, but if the usd price of monero rises and the borrower is being paid in usd then they are going to default and you will loose the xmr. The only way I could see to counteract this would be to lower the Monero payments per month, but then that would take even longer to be repaid.
Well you don’t want to lose Monero and you don’t want to lose fiat, but you can’t have both. XMR isn’t a stablecoin.
If it matters more to you that you get your XMR back, then require XMR payments. You need to include the XMR volatility as part of the interest rate calculation.
If it matters more that you get your fiat back, then require fiat-equivalent in XMR payments.
Or, demand you get either XMR or fiat back, whichever is higher. But I don’t think a borrower would like this. Tesla did this when they let you pay in BTC; Tesla reserved the right to refund you in whichever currency was cheaper. For the consumer, it a bad deal.
I don’t care if I lose Fiat, but I do not want to lose Monero.
Then you need it factored into the interest rate you decide upon that volatility may cause the price of XMR to get so high that your debtor would rather default than pay the debt.