file-create-directory appears to be the only file-* interface that accepts permissions, documented or otherwise. Does anyone have recommendations on how to manipulate filesystem permissions via zapi (even something via system-cli)?
The obvious question - which permissions? There could be at least three disjoint permission sets - Unix, NTFS and NFS v4. NTFS could be changed using fsecurity command invocation (via system-cli). I do not know if it is possible to directly manipulate Unix or NFS v4 permissions.