I have a good update on the filesystem. It seems that there are only two changes: the magic of the superblock changed from SFFS to SFS!, and the superblocks start at cluster 0x7C00 instead of 0x7F00 (and continue until the last cluster, so there are more of them).
So it is extremely simple to change existing tools to work with it. For example, I took Wii NAND Extractor, and only had to change one line to get it to work:
View attachment 82037
So it should be simple to create a tool to fix bricked CBHC full nand dump...