With bitcoin it's actually possible to monitor how much of your funds are left as a reserve with your bank.
If you transfer 100BTC to your bank account, and have selected a 50% CCR option, the balance of that account should never go below 50BTC.
Sure you might not get much interest in this case but you can chose your risk vs interest payment on an individual basis.
The account/wallet monitoring of the blockchain could be an app you run yourself  or a 3rd party service.