Given that Musk is expected to be a trillionare within the next couple of years,I reckon there would be enough liquidity for him to open a bank.
Its not his wealth its cash that would be able to derive what you are thinking. Bearing in mind that a large % of his assets are still made up of shares in Tesla (something like $90bn) and SpaceX (something like $170bn), the expectation of growth in his assets is from these investments.
Now, if he wanted to liquidate his assets, tell me, what would happen to the share prices of those businesses should Musk sell a significant sum??? What would then happen to his "wealth"?
Just on your "business model", it shows a distinct lack of knowledge of how banks run, how they earn profits, and how they provide liquidity to remain open, but I'll leave that for you to figure out.
