You would have to use the powercms template concept and create a recordset to loop over to handle the ability to add new pages to a menu... it isn't built into CMS builder in this version so it requires a little hand coding to create the correct recordset SQL just like powerCMS, but it is possible. (we have a functional example of this in powerstore and I've posted the necessary recordset sql in previous powercms threads)
The admin area can be completely re-skinned.