The single most important feature (to me) that Apple should add to the iOS 11 Files app is to mount USB memory sticks and hard drives when connected via the connection kit/adaptor.
I'd love for them to go USB-C, then this would make mounting essential and open up so many cool possibilities and devices. Much like MacOS it should just pop up as an icon on the home screen. There are some things, I seriously don't get with iOS and not having proper USB support is one of them.