As I was showing a friend how the song request form on the website he suggested this and I really like the idea.
When there is no live source connected to the server and a song request is made. There should be a pre made outline that admin of the station can write and is read by a TTS (text to speech) that says something along the lines of;
"Coming up next is a song that is dedicated to" (TTS from song request forum) "and thanks for listening to this station"
Also would be cool to even play a single preset track or sweeper before each request so that it is set out as a request.

I know this post is old, but I had a friend who had this service. It was a "competitor" panel Centova, but much less "expression" and nothing known. But it was revolutionary. Api had a huge list. With this system it was possible to create an entire radio 100% automated and robotized where even the announcer was the voice of google. It was exactly this way. We could customize all lines and all we wanted. It was a dream. But the owner gave up system, closed and refuses to sell.
My dream is to see the Centova so.

Sorry for my English. I used the google translator and do not fix the errors.