As I said in another comment, you can handle the legacy systems by giving a mount option that transcodes filenames using Latin-1. (Choosing Latin-1 because it's

As I said in another comment, you can handle the legacy systems by giving a mount option that transcodes filenames using Latin-1. (Choosing Latin-1 because it's a trivial mapping that doesn't require lookup tables). UCS-2 is easily handled by WTF-8 (i.e., don't treat an encoded unpaired surrogate as an error). The reality is that non-UTF-8 filenames already break most modern software, and it's probably more useful for the few people who need to care about it to figure out how to make their workflows work in a UTF-8-only filename world rather than demanding that everybody else has to fix their software to handle a case where there kind of isn't a fix in the first place.