In Blender I'm working on tetragons (in special cases there are n-gons), but when exporting I always check "triangulate faces" option. And even if I would forget it, @tomaszkax86's converter can triangulate faces too.
Models always should be triangle-based in real-time rendering (if I know correctly, this is more optimal for GPUs). More-than-3-edges models are easier to modify and they should be used in source files of models.
Current model format is anyway to replace, so digging with it doesn't really make any sense. New one would support some more advanced multi-flags system instead of old mono-state system.
Oh, that's rignt. I afraid smooth shading must be implemented to rendering engine AND to model format. Then you could only select what edges should be smooth or flat in Blender and converter should translate this correctly to GOLD's model format.
@tomangelo : I just tested all models from your repo how they look in the game. Well, there's still a lot of work to do before release. First, turn on smooth shading in most meshes. Some models look good, some isn't because I can see every polygon even if they have texture on. Second, some meshes have no faces on both sides (PowerCaptor dish for example). Third, there's still some round plates instead of octagon what we decided to officially use. http://i.imgur.com/a5wPipo.png
Currently after half of the work with the textures of the objects that I done all I can say is that I won't be able to deliver all usable sources to GitHub. Possibly this will be only XCF file and some updated SVG's. Rest is purely raster and currently I made so many complex changes combining @Simbax and @Adrian assets into one as best as possible looking hybrid.