Hm...that's interesting. I think most people use Z (just do anything, attack, roll, spotdodge, whatever and hold down z; once you finish, you'll be light shielding), though I think a trick like that would make lightshielding easier, more accessible, and all around more useful. Nice :o
Oh, and you don't have to plug your controller in to do that. The GCN controller has a built in button combination that has the same function as unplugging and plugging it back in, all without moving from your chair. Just hold Y + X + Start for about two seconds and it will "unplug" the controller for you. upon release of any of the three buttons, it will plug the controller back in.
I do like that idea of yours. A lot.