Quick update for tonight, after a busy 4th of july week-end. I can create links between 2 CADCloud saved document, and properly save the Document which contains them. It has been easier than I initially thought to implement. I need to clean the code now, but this is just amazing to see it working !
FreeCAD is already a desktop app. All I was doing was bringing it to the browser in a way that might be useful.
I mean the Web part. FreeCAD has the browser shipped with Qt. So you could start the web server as a part of FreeCAD initialization on open it inside FreeCAD. Have you checked out this thread: https://forum.freecadweb.org/viewtopic.php?t=48611