the ability to either duplicate a panel or a better experience would be to save a panels config in its current state and give it a name. when you add another desktop panel it would show you the default current options(application menu bar, default panel, empty panel) and any that you have saved under the specified name you had given. you would be able to delete these as well. maybe with a simple "X" next to those user created panels in the context menu itself or in the system settings under an appropriate location.