On the overlay of the announcement and the walkout... that is pretty complex overall because of the coordinated volume and timing sequence. In my tests, the user would need the ability to configure both of those options on a song by song basis to get quality output and I would somehow need to gracefully preclude using Apple Music songs with that option because I cannot independently control the volume of the player Apple requires I use to play those. I have to actually snapshot, fade, and restore the volume of the whole device for those songs. Ugly, but it works.
Over the next few weeks, I'm going to analyze the usage mix between Apple Music subscription songs and unrestricted song files to see what the mix is. My last three day snapshot puts the Apple Music percentage around 40% but that may be a spike because of the recently added support. If there is still a reasonable percentage of people using unrestricted song files, then I will take a look at how to mix the announcement and walkout song as an advanced option.
Thank you for the suggestion!