I would really like to be able to give webpages access to a real local file/folder. It's one of the main barriers to using web apps as production apps and is IMO one of the drivers pushing everything into (generally proprietary, locked in) cloud storage.

Obviously the permissioning model needs to be thought out here. It could perhaps only be available to "PWA"s that have been "installed", only on https sites, and only once explicit permission has been given, etc.

But it's so cumbersome to have upload/download be the only way to sync files into a web app.