Just in case someone ever needs to export a model in the form of meshes, the lion kingdom provided an example script.  The mane requirement is recursively descending into App.Part objects, applying the transforms, flipping normals, & making some polygons double sided.  It shows how to create an identity matrix & multiply it by part transform matrices.

https://cdn.hackaday.io/files/1380505906331200/export_bfs.FCMacro

People seem to be applying textures in Godot.  About ready to give up on FreeCAD after the BFR model & give Blender another go.

Watching this video, the Falcon 9 model in KSP has gotten a lot more realistic, in the last 3 years.  It still may lack a block 5, but it's far more detailed than a lion could ever get the BFR.  It now has an empty outline of Fl*rida & some kind of launchpad, but Orbiter had LC-39 fully modeled 15 years ago.  Except for the Falcon 9 model, Orbiter looked better than anything later.  

A true to life BFR simulation won't ever serve any purpose, compared to KSP.  It would have to be arcade physics with a campaign loosely based on traveling to other planets.