I’ve had similar backend projects where I setup a reverse-proxy to a backend, along with the frontend dev server, to allow the full site and api to run in the browser from local host.

It’s not the most graceful setup, but it works if your backend build isn’t as flexible as you need.

If you're talking about something like Django where you would want to serve frontend JS from a static assets directory, you would have to output a build bundle into your static directory. You would not get hot reloading that way, though.

You could yes, however you’ll probably have to write your configuration from scratch. You’ll have to define the JavaScript entry files (those that call the others) and put that into your HTMLs. Depending on how many scripts etc you have this might be a lot of work, but this should optimize your JavaScript to ist what you need.

I don't think Webpack is designed for that use case, it is pretty apples and oranges