I have an idea for a new gedcom import module.
I have been working with the GedTool program for years. It allows you to enter data in an Excel table and use a mapping file (Excel table) to control the conversion to a gedcom format (5.5.1 and 7.0).
Perhaps it would be possible to implement something like this in Gramps, using an Excel table to tell the Gramps import module how to handle the individual entries in the gedcom file.
You could modify it so that importing gedcom files from different programs works without problems.
You could control the export in exactly the same way.
In Gramps, all you would need to have is the basic module that controls the import and export with the Excel table.
Feature Request number 0013648
https://gramps-project.org/bugs/view.php?id=13648
Just a thought of mine…