I'm not a developer, but it seems possible to create an app that would add external USB support to the Files app. I'm sure it wouldn't make it past the review process to make it on the App Store (or someone would have done it already). But if a personal were to develop it on their own, couldn't they load it onto their own iPad?
If that's true I'd crowd fund an open source project to do that.
If that's true I'd crowd fund an open source project to do that.