We have an existing MP3 player hardware, on the next version we're also building an accompanying app that would connect to it through Bluetooth and display content of it's screens along with control buttons.
Sound would still be generated on the physical device, we just need to build a remote control app.
The problem is the screen on the mp3 player is small and hard to see from a distance.
The user is standing on a stage and the player is connected to a sound system off the stage.
The solution is their tablet or phone showing a larger, closer screen via this app.
If I later want to expand the apps to do more ... such as transferring downloaded music files to the mp3 player would you be able to add those features later?
I have gone through the requirement and I clearly understood all your requirement
Also the feature for transferring files from app to mp3 player is also possible.
Let me clear about your thoughts and then we will move further on your interesting project.