Module support?

Looking at the loosely coupled system of CodeIgniter, support for it could and should be added. I do think the added support should not effect how CodeIgniter functions at this moment. Direct routing to a module for example is not needed in my opinion.

I have done this with my Simple HMVC. Only extending the core loader so the ability to use modules is available, but not required.

I think you side-stepped a lot of the issues in HMVC by making the "controllers" in your modules not extend CI_Controller (or some replacement class) and not making them routable. In some ways, that enforces the separation between MVC controllers and HMVC controllers, which is good. However, if you don't have the option to create an MVC controller in a module, then a module can't function without an external controller. While that has some benefits, it also starts to degrade the benefits of modular organization of the code.

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide