I totally understand your concern with wanting to make it so the player can't easily delete their save files. I still think deleting the save files is out of the way enough that the usual player will not delete their files.
I do like the idea of making your own music although my first impression of it was that it was a strange heart monitor and I didn't fully understand how to do it. In this format of game I probably would have liked to see the player listening to the character humming their own music that was premade but the player could decide to hum or not by pressing the A button.