Manifest v3 hardened down on what is doable with code execution and remotely hosted code: https://developer.chrome.com/docs/extensions/mv3/intro/mv3-migration/#code-execution

Following scenario: I want to create an extension that allows the user to add additional functionality into the extension by explicitly specifying javascript files on disk and giving permission to those files (for example through HTML5 FileSystem API, file picker, file:// urls, or maybe just a config file). They are not distributed with the main extension.

These files may also contain some UI code written in a UI library like React or Vue, which should get rendered into the main application window somehow. The main window would also pass information about the extension context into those components.

I understand that there is the sandbox that can be used to execute code - https://developer.chrome.com/docs/extensions/mv3/manifest/sandbox/

I know how to do these things in normal applications but is what I want to do somehow feasible with v3 and the new restrictions on code execution and external code loading or am I hitting a brick wall here?