Well the region problems come from 2 different things:
1. the discID
An unmodded disc channel only loads games with discIDs from its region. Gecko OS and Gamma look at the discID to determine which video mode to use as default, that's all they do with it. They don't care if the region matches or not.
2. the video modes
That's a lot more complicated. If you mod the disc channel to load games from the other region, it's still the question in which video mode you launch them. If it's your region, then you get problems with about 50% of the games, because these games only accept video modes from the region they were made for.
If you patch the disc to the other region(completely bullshit in my eyes), then the disc channel accepts the disc, but you get the video mode problem with 50% of the games and if you launch the game with a loader, it tries by default to launch the game in the wrong video mode.
Why do you want to change the discID? If you use a loader, you get the less possible problems without messing with the disc.