Don't really want to drag this on since it has been answered, but does anyone have any knowledge of what methods have been tried to accomplish this? I'm just curios as I use to trick the original Wii using my one external enclosure before we could switch partitions.
Edit: The enclosure always mounts the second partition because it originally had software on partition 1 that was "undelete-able". Also, I am assuming simple 2 partition setup was already tried as that's what OP tried, so you can count that method out.
I understand the contents are most likely encrypted, but I was thinking of using my 16gb pen drive to format with the wii u after blanking it to 00's, making a sector copy and then making a partition after the end of the wii u copied sectors on a new disk.