[eluser]WebMada[/eluser]
As CMS, I always have to develop modules like themes and plugins (addons) if I want to customize it.
Develop themes is not hard because it is codeigniter.
But develop addons is a bit harder like with other CMS (Wordpress, Drupal, etc.)
I doubt to totally migrate to Pyrocms/Ionize from Wordpress because all CI-based CMS don't have much documentation.