So while browsing around Wiibrew I was looking at Gamecube Homebrew Launcher and noticed it installed a MIOS and has access to the front SD slot. Maybe I read it wrong. I was under the impression that GC mode disabled the SD and USB slots. If this is the case than perhaps this code could lead to not only GC running the SD slot but also be a hint on how to get USB support as well. SD would be fine too, because you could put several shrunk GC isos on a SD card.
Hope this helps someone
Hope this helps someone