From your first post:
Either way.
Headers exist because of one of very important features in C++. *Every *.cpp file is treated as completely separate thing from all the other .cpp files..
Lots of C++ libraries actually rely on that behavior and use multi tier header system to control visibility of this or that feature.
You might want to tell people why the heck did you want modules in the first place.
If you want “faster intellisense”, there are other ways to go about that. QtCreator was pretty **** fast last time I used it, for example.