extensions for an existing CI app (hooks)

Hi,

Let say, I have an CodeIgniter application that's going to be deployed in many sites. They all have the same needs (hence they use the same app), but they also have specific needs.
Is there a way to use "extensions" on a CodeIgniter application (the same way, we use "plugins" in WordPress, for instance - not the same as CI plugins) ?
Of course, I could use CI librairies to add the code, but I will still need to modify the existing application (for instance to add a new line in the application menu). I don't want to modify the CI application otherwise, I won't be able to release easily a new version.
In WordPress (and others) they solved this, by using hooks.
Is there something similar that could be used in CI ?


Thanks in adance,
L@u