As I'm spending some time back in the land of low-level C, I'm trying to fully get my head around best-practices for header files and code organization, so I thought I'd toss out some questions ...

It isn’t very complex — the whole thing lives in one fairly large C source file but it can scan a directory and create header files for everything.

Basically once you've put a using namespace std; in your header, and someone has included your header, there's no way to undo the using. This can reduce your options when a name conflict occurs.