I like the workflow, thanks for posting. It would be really nice to modify it to automatically select the input I care about, rather than being forced to select. For alfred remote users, this would be a great benefit (we're trying to do away with keyboards and mice). If I run the workflow from my remote, I'm trapped because I need to switch to a different app to make the selection. Regardless, it is much sexier to have it complete the task as desired.
Obviously I would need to set the name of the audio output by modifying the workflow, but once I have set it and save as a new workflow I'm done. I would create as many modified workflows as output sources I care about, and now I just press a button on my remote to switch between them.