I’ve written a light wrapper around MPIIO a while back to do Single-File Multi-Process IO. It might be aligned with what you describe but it might need some adaptations.
Now, this might be quite beyond the scope of the current GSoC project.
If you are interested in having such parallel IO library polished in a broad manner within stdlib or as a small standalone Fortran package let me know to discuss about it. This thread contains many good resources about that topic MPI IO or not to MPI IO?