I just replied in the “pawmasher” thread here.
In short, one solution is to have a clickable icon in the status bar which denotes your playback mode. The modes would be “Play now”, “Play next”, “Add to queue”, “Radio”, and “Bring up the pawmasher” (which should be the default). Clicking on the icon cycles it through these modes.
This is unashamedly stolen from the Squeezebox world and it works, and it works for everyone’s different use cases. Why reinvent the wheel?