A client has asked me to redesign their existing WordPress site but to keep the majority of the data (blog posts) in the new theme. In the past I have used plugins to hide the theme I am building from the public but to show the new one to logged in users. My problem with this new case is that the client wants completely new headings on the menu.

So my question is this: Is there a way to make the menu theme specific so I can fully develop the new theme without impacting the present themes menu?

Thanks for any help on this issue?