I tried this out and it worked great. Is there a way to access the Z button though?
No but I think if you have a Gamecube controller in any other port the Z button on that will still bring up the menu.
Edit: On another note, with all this 240p Gameboy Player stuff going on, has anyone ever tried 240p previously via something like the Extron Emotia on the Gameboy Player? If so, how was it?