Seriously, good crypto should be limited and there is no way you are going to accept someone lending you bitcoin with a "bitcoin certificate".
Is this not exactly what happens with people holding tokenized bitcoin, wrapped bitcoin, bitcoin on Ethereum, on Tron, on Binance Chain, or any of the other "not actually bitcoin" bitcoin tokens? Someone, often anonymous, promises to pay you real bitcoin in return for your fake bitcoin.
There is no way you can borrow more than it exists if you have taken even the minimum required time to understand what you are doing.
If you actually hold the bitcoin yourself, sure, but if it is tied up in layers of DeFi nonsense or something similar, wrapped up in altcoins, stuck in smart contracts, held by third parties, etc., then all that goes out the window. As I said above, the only way to avoid fractional reserve altogether would be for everyone to hold their own coins, but we both know that's never going to happen.