I'm willing to pay someone for their time to develop a way for rdio-scanner to directly input multiple remote streams as individual talkgroups. Any developers out there up for the challenge?
Looking at rdio-scanner, I don't think that you're going to be able to do that within the framework of the program. rdio-scanner isn't really a feed player in the way you think of conventional feeds, but more of an mp3 player in that the program that sends the audio/data files does the recording and then sends the recorded audio/data to the rdio-scanner player-it is not a live stream. Each transmission has its own *.mp3 designation, meaning you would have to have the source providing the feed to rdio-scanner send it to you as well, which is not the rdio-scanner audio url.
Knowing the problems that Broadcastify has encountered with the piracy of audio feeds, the Broadcastify Calls platform, which is very similar to the rdio-scanner concept is brilliant. Couple that with their rotating URL technology and it goes a long way to defeat the app developers that are/were stealing the feeds without providing any compensation to Broadcastify to offset the cost loss of not getting the ad impressions on the feed page (Yes, I know they no longer do it) or the potential to put their paid services in front of the listener.
Could it be done? Maybe. As I see it looking at the various rdio-scanner compatible VOX recorders, you would have to get the feed provider to send the feed to the receiving URL of your rdio-scanner instance as well as the one they are currently providing it to, which would require them running an additional VOX recorder program, the API key for your rdio-scanner instance and most likely having to set up an internal audio cable program on their feed computer.
For those feeds that still use the conventional "always on" feed style, I think your best bet is ScannerLive and Rob refining the http/https issue.