Peter has opened a new discussion thread to discuss the ForceProvider API: Desired features / requirements for ForceProvider APIs
Note, though, that the issue 4662 was about command line entry points, which are a very different topic. Maybe someone can correct me, but to my knowledge there are no near-term plans to update this facet of the software—that is, to (1) reexpress the command line entry points with API-friendly and maintainable patterns, and (2) export such an API with the installed package. You might be able to do what you need with the installed gmxapi headers. But if you need to interact with the grompp pipeline, MDP parameters, other traditional input files, or the command line option processing machinery, you will have to fork the repo, borrow headers, patch the build tree to add your own command line entry point, or submit source code updates.