There is a way to use Priiloader to automatically boot to the homebrew channel rather than the Wii menu, IIRC.
In Priiloader, you go to Settings > Autoboot, I think is how it works. I'm not at home or I'd double check. Let me know if that works
Aside from that, I don't think there's a way to control the Wii Menu itself from a gamecube controller.