While we're at it we could go back to a monetary standard backed by physical assets. Not necessarily gold, let's say a basket of everyday assets (wood, wheat, iron), so that the value of currency is tied up to the basic needs of a society. If you want to convert from fiat to these goods, you can do that.

You can handle banks misbehaving and defaulting on their obligations with a competing system of private banks, third party services reviewing and auditing these banks and by paying a private insurance tied to the amount you own.

Given that generally banks will make money with your parked resources they could be able to pay for the private insurance from the interests on your money.

I don't think cryptocurrencies are the answer, they're a technical answer to a political problem and governments will probably just squash it or find a way to benefit from it.