Hi xor, the answer is in the error message: "Read-only file system". This has to do with how TCL works and has nothing to do with xfe.
The contents of /tmp/tcloop/ are mounted extensions. Extensions are squashfs archives. Squashfs is read-only.
If you need to modify properties of the files or directories inside acl.tcz or any other extension, you have to extract the extension, make your desired changes, re-create the extension, then replace the extension in tce/optional/ with your modified extension.