The manual is not limited, it is the omniobjcopy command itself. Most of the Object Copy operations that can be executed from GUI can't be done from command line. If you're not able to make it work with the available command switches you need to run it from GUI. It is simple as this.
FYI, BRICK has a module called space claim. Not sure if it already generates the necessary omniobjcopy commands, but it might be worth looking into it.
Please use the Accept Solution button next to my post and assign a KUDO (thumbs up icon) if this works for you.
Regards,
Sebastian Koehler