Hi @garnet​ ,

Apologies for the late response. You may already have an answer by now but I'd like to share a response for visibility. The security model for FME Server does not track ownership at the workspace-level yet. FME Server only allows the change of ownership for Repositories and not individual Workspaces. You can re-assign ownership of Repositories in the FME Server Web Interface: User Management > Items > Repositories. If you remove or delete a user from FME Server, you'll also be prompted to transfer ownership of the items they own. 

Here is a similar idea on FME Community. Please vote on this idea and comment your use case if this is something you're interested in. 

Thanks,

Kezia