i feel you, the ps2 had freemcboot, and i feel really sad that the gamecube doesn't have a similair thing...
aside from modchip (there are several types of modchip from what i know, some are for the drive, others for the bios)
there are discs exploits as well.
one method being the sd media launcher or similair disc loaders
the other is exploit trough a game. there is a wide selection of compatible games games, the pokemon collosseum or xd being an example, i think smash bros as well..
you just have to have a hacked save file in your memory card (can use a wii to move the save) and it will boot the thing of your choice for example swiss
sadly, this will have you to use a boot disc every time you turn the console on... and if you want to use burned discs, you will have to swap..