Sandboxed execution is definitely one aspect... But IMO, this is still not secure enough for vibe coders. They will want to have data-driven apps to share among small groups of people, then the security of the sandbox doesn't matter if they expose some external endpoints and if the access control logic which guards data is flawed.

Even if each user gets their own sandbox, they will still want to configure different access rules for different kinds of data which they host.

That said the idea that each user could control and host their own data is interesting and could work. I imagine you could have apps which link data from many different user sandboxes via remote foreign keys.

You could have a centralized data schema controlled by the application owner but the data itself would be held/scattered across a large number of sandboxes.