I'd love that too, but I'm not sure it's even feasible or possible, at least in the EU country where I live. I, like most people (I think?) need to file taxes each year, and those include my new positions, or what positions have disappeared, including how much I have in savings. And, the only way for me to keep savings without losing money, is to keep it in a bank, so it's again not private.
Feels like "private finance" been dead for a long time, unless you start using cryptocurrencies specifically for privacy, like zcash, otherwise you'll be having non-private data at least somewhere.