That’s basically leverage and very risky with such a volatile asset. Doing it on your own risk is fine if you like to, recommending it to others is irresponsible.

Furthermore no bank takes BTC as collateral, so you have to go the DeFi route which is a absolutely no-go. The risk of losing your whole collateral is quite high this way.

Or do I miss something? How do you borrow fiat against your Bitcoin?