Don't take me wrong, but is it really worth it making a whole new CMS from scratch taking in consideration the amount of highly advanced CMS's already out there? Wouldn't be just smarter,more useful and time efficient to make some adaptations (modules,plugins,etc) for Joomla, Drupal, etc ?
Aren't you going to use AJAX as well?
hope you're not offended,just my 50cents.