Currently, when writing a custom C module, you have to make edits to the Makefile and mpconfigport.h.

This means that, that to distribute a custom C module, you can only do so within the context of a fork of the micropython repository. If I find one person who's written a micropython module for vectormath, and another person who's done a particular communication protocol, then in order to use both of these modules, I have to have a fork of the micropython repository and somehow merge in the code from both of these. There's no easy way to share custom C modules libraries.

I think this contributes hugely to why there are very few custom C modules publicly available for micropython - it's simply too hard to distribute them in a meaningful manner.

Ideally there would be some way of loading compiled libraries (similar to how ctypes allows importing .so files). This is probably impossible in a useful way, but it would be ideal ... allowing drag-drop loading of C modules.
A more realistic way would be to allow some way for code in subdirectories of the ports folder to be able to add their files to the Makefile and mpconfigport.h file at compile time.

I'm willing to invest some time into solving this problem, but was wondering if there are other solutions I missed, or if someone has a better idea about how to solve it.