I did check pandoc a few years back, and at least it didn’t look like it had sufficient information for citations and I thought we handled a lot of the imports better with our paste analysis. Likely pandoc has improved since then. Maybe the easiest way to get a number of reasonable importers is to just write one importer from pandoc’s main format?
The fidus file is basically a zip file with some json files inside. The format changes with every Fidus Writer version as we add new features (and in seldom cases remove some). We thought once that we would switcht o a standardized format as the main file, but that doesn’t really work because it restricts both what features we can add and remove to the editor, and it doesn’t allow us to do fixes to the way we store certain things in newer versions.
For example, if in version 2.2 we add support for 5 new languages in which we let users store their documents, we will then need to go to the committee that controls that file format to get those 5 new languages added. Or we added tracked changes in version 3.5 and if we did not have control over the file format, we would then need to wait for te standard we had chosen to also support that before we could release.
For that reason we keep Fidus Writer as the native fromat for Fidus Writer, and we make sure that users always can import their older fidus document, but it’s not a good idea to use it as an interchange format.