The solution is easy: Just clone a disc. The idea: Give the Wii disc an other ID and play it with an USB loader. Enabling the online mode is also possible.
This article decribes how to create a clone and how to enable online mode.
Example: »wit copy source.iso dest.iso --id K«
The option »--id K« modifies only the first character of the ID,
it is set to
I prefer
If you want to change the ID of a already copied image,
use the
»wit edit image_to_edit.iso --id K«
You can also add an image directly to a WBFS partition:
»wwt add --auto source.iso --id K«
The source can also comes from the destination WBFS.
Assume
»wwt add --part /dev/sde5 --id K /dev/sde5/RMCP01«
If you want to change the disc title too, just add the option »--name "disc title"«.
»wwt rename --auto KLONE_ID6=ORIG_ID6 --iso«
and for Mario Kart Wii:
»wwt rename --auto KMCP01=RMCP01 --iso«
The option --iso means: Modify only the ID of the ISO, but not the ID of the WBFS header.
This also works for WBFS files on FAT or NTFS.