I have build a simplified version of wordpress admin without all the features and stuff, only posting some specific custom post types and pages. This simplified version addresses a specific role on my normal wordpress operation (since admin is such a fuss to customize), but it lacks some things, such as using the plugin administration from the normal wordpress wp-admin. The wp-admin, still works for administrators only, but they are out of the loop for what I want to implement.
Given the fact that my clients now want to use an internal private messaging system, what are my options here?
Basically I am talking about (backend) pages in the same domain such as wp-admin that have wp-load.php, checks for roles and specific users, custom designed and inside them I want to use, for example, the wp private message plugin or the messaging plugin from wpmu.
Is there any other customizable php class that I could use?