I'm not looking to design parts, only provide a stock. Perhaps I'm not familiar enough with KSP (like stock upgradeable parts), but I'm only looking to keep track of part count and that's it. So { {name=partname, count=count} } should be enough. A few other parts might be treated differently, like procedural parts using raw metal instead of a specific part, but that will be on the KSP side rather than the data exchange file.
Part of the mod package will probably include a recipe generation utility that parses KSP parts to generate Factorio recipes so this mod will support a variety of KSP mods.
Back to the subject of KCT, you may be able to simplify the UI by forcing obsolete parts to be refurbished to their new version so you don't have to handle selection of old versions.