I just love the idea of going around creating accounts at multiple different banks for storing of parts of the key.

Then, when you're finally ready to access you funds, creating appointments at all those different banks, driving to them all, and then finding out enough of the keys are completely missing that you now cannot access any of your funds:

https://www.nytimes.com/2019/07/19/business/safe-deposit-box...

Or... you know... you could just store your funds in one or more bank accounts.