Strange, never heard that one before....
You could try the older version of ARC, it doesn't work with wii motion + remotes, and you will have to make sure to change the video mode settings back after auto adjusting other settings
https://github.com/modmii/modmii.github.io/blob/master/temp/ARCmod06_Offline.zip
Follow the steps from this video, except pick 249 instead of 236 since u don't have 236 installed
If this STILL doesn't work, the only other way of region changing is using ohneschwanzenegger, providing it with a nand backup and/or keys from your Korean wii, and having it construct a different region nand.bin for u that's compatible with the wii in question, then restore it using bootmii. Very important though, make sure you use KoreanKii to remove the Korean key before doing this!! The Korean key is in the seeprom, not just the nand, so restoring a non-Korean nand backup won't remove the Korean key from the seeprom, and if the Korean key is found on a 4.2 or 4.3 non-Korean system menu, and a stock ios70 or ios80 is installed, you will 003 brick. For this reason, you should remove the Korean key before hand, and maybe build a 4.1 nand (instead of 4.2 or 4.3) using ohneschwanzenegger just in case to be extra careful.
This isn't without some risk though, unless u have bootmii installed as boot2, then it's not as risky