[Zarkonnen]

This is more or less the same thing as a steganographic file system, I think? https://en.wikipedia.org/wiki/Steganographic_file_system

[remram]

This is only a steganographic file system. If someone finds your secret, there's nothing deniable about it. Hidden is different from deniable.

If you're trying to hide the entire fact that there is secret, encrypted data on your secret-encrypting device/drive, I am not sure I get it either.