Create a Drow Down Menu New Feature

Our CMS adds new pages using Horizontal Top Nav Menu system that it does not escale. We need to allow users to add more pages as a Drop down menu options so that the site number of pages can grow if needed. WHAT WE NEED: 1-) Add a Drop down menu options.. 2-) Create a warming message stating that reads (below) if they try to add more than 6 pages. "you have exceeded the number of pages that can be added. Use the create drop down option instead to add more pages. 3-) Test it make sure that it works. 4-) resolve any bugs found. OBS: See screenshots attached. By the Way our CMS is written in PHP and uses msql. NOTE: You will be given higher priority if you can make this into a a plugin that can be easily added to any other mock ups we have.