pyshellext uses MIDL to generate a header, whose only purpose is to define a class GUID. MIDL generation step can be replaced with a simple #define. This doesn't really matter for VS, but other build systems (CMake, probably Meson too) will benefit.

pyshellext has separate .def files for debug and release builds. One .def file is sufficient, because LIBRARY statement is optional.
Using __declspec(dllexport) isn't an option, because Windows headers misdeclare DllCanUnloadNow and DllGetClassObject...