The OP has a solution which is looking for a problem.
In other words, he is full of crap.
You don't need a smart contract to accomplish this. Bitcoin is doing it already and it is the ultimate smart contract. It is decentralized, it can't be seized, it deflationary. Bitcoin is the ultimate decentralized world bank and you are participating whenever you use it. You just don't need anything else. Don't make this unnecessarily complicated.
At first glance, it seems logical, but if you drop deeper, it turns out that the bulk of all bitcoins are in the hands of a very narrow circle of people who manage volatility and increase their share even more with the help of manipulation. To counter this, there is currently no insurance, so banks do not lend for fear of losing their assets.
In my project, this insurance is available for banks.