As for interacting with local files: I imagine a CLI tool that spawns a webserver that will serve local notebook files and perhaps the files in folders you point it at. Or: you generate a notebook file with the data baked into it (as a JSON blob or something).
As for security: I think the browser sandbox is a lot more safe than running Python (Jupyter) with a lot of dependencies you will have to verify.
And finally: you need to be able to get the data into the browser. For a company the most 'scalable' would probably be self-hosting Starboard and (setting up CORS to) allow reading from various datasources from your internal network, or otherwise authenticating the requests from notebooks.
Another thing that has worked well for me in the past with other web tools: support drag and drop. You drop in the file you want to visualize.
In the end Starboard notebook is a tool for creating a small website that you can instantly share, without needing a backing Python server always on, and without the need of any build tooling (webpack, what have you). It's good for small web tools, articles and tutorials. I hope this makes it a little bit more clear!