I'd like to see "lock-step" between the iOS and Android versions of the Fly app - there are things that work differently (or not at all) on one platform or the other. Examples that come to mind are Disable Sideways Flight and writing photo/video capture location/orientation to the flight log. Neither appears to work in the Android app.
Beyond that, Litchi-like waypoints that I don't have to fly to first just to program. More flexibility in assigning what the Fn button does. Extending the digital zoom capability to photos.
And the idea of being able to turn the gimbal off from the app so that filters can be changed was one I hadn't seen until reading this thread, but it's a good one.