A file is moved to quarantine with a tombstone left behind, and need to customize the content of the tombstone file. Currently it says "Please contact your IT administrator for further assistance".
The contents of the tombstone file can be customized when using the local Cloudsoc Policy (Cloudsoc Protect Policies) using the "Custom Response Template".
This solution works whenever the preserve content option is available, just keep in mind that most of the content inspection response actions are performed on the DLP side, for this reason, the preserve content option is not available on all the policy types.
Here is an example of a Tombstone which replaced the original file