Yes you can - but you need the outer volume to have fat style file system where the OS won't write randomly (not sure which of the *nix ones is suitable for tha

Yes you can - but you need the outer volume to have fat style file system where the OS won't write randomly (not sure which of the *nix ones is suitable for that) at the higher addresses. You basically say - from this address on is a hidden volume and there is new volume header with new master key that needs to be mounted separately.