Before gmixer was deprecated and orphaned, I was able to use it to access low-level settings for my sound card. Now I can't. I'm left via the sound settings applet with access to only a single input volume slider and a single output volume slider. I can use alsamixer to get access to the low-level settings, but I shouldn't have to. I don't know whether the decision to replace gmixer with a less functional one was made by Fedora or the GNOME development team, so I'm starting with Fedora bugzilla. Feel free to upstream if that's more appropriate.
'Expose all settings on every sound card' is not a goal for the gnome sound panel. As I said on the list, we are interested in actual use cases where our controls are insufficient - please report those upstream. But 'my card has a low-level setting that is not reflected in the ui' is not a use case I would consider relevant.