Hmm, actually _PyImport_GetModuleDict() isn't needed to solve the startup issue. It's still rather internally focused but the same could be said for PyImport_GetModuleDict(). I guess I'm still not sold on adding a new public API function for what amounts to a rename of PyImport_GetModuleDict().
Furthermore, wouldn't it make more sense to keep it in the PyImport_* namespace? Perhaps we could set the precedent that explicitly-arg'ed functions should be in the PyInterpreterState_* (or PyInterpreter_*) namespace?