The Use Case is that I might want to play alternative streaming sources to my Roon end point which doesn’t support the requested protocol (for example, a Sooloos endpoint doesn’t act as an AirPort speaker). Rather than having Roon support the protocol directly (which might involve licence / questionable legality) the core could have a generic RTSP/RTP or HTTP input port which is available when nothing else is being played. From there you could have another application act as a protocol converter which makes the Roon playback pipe available to other clients.
This is sort-of like IP radio except the core is passive and an external client asks to use the playout pipe.
Make sense?
Ian