"Speaker" overlayed onto backend radio playlist

Hi everyone!
First off, this is an awesome software.

As far as I see, WebDJ always interrupts the backend playlist and it is thus not possible to use Web DJ microphone to speak over the already running backend playlist. Something like a speaker on a radio that cuts in the program to say something while the music is continuously running (with a lower volume, in the background, while he speaks)

Is it possible to customise/upgrade the WebDJ in this sense, or better perhaps, create a new kind of feature "Speaker"?

If you would kindly point me in the right direction or any docs that explain where it would be best to try and implement this kind of feature, I would like and try to contribute to this project