Just as a thought:

I can imagine, that the fbx file format is relativly unoptimized for games because it allows a variety of features you'll never need in - even a modern - 3D-Game. So there is a lot of overhead in this file format for the 3DGS-Engine which will slow down loading (probably to a very high extend). Therefore it's useless to load FBX while runtime.

So even if the loading time would be just 50% higher as they are for the optimized MDL file format, don't you think, that this time is worth to save at runtime and just convert the model?

BTW: An Instruction like this: ent_create("test.fbx","test.mdl"); does not make sense at all. At least at runtime it would just screw up your loading-times.

greetings,
Tech

PS: I've never tried out the fbx mdl converted, but if it works correctly, as already said, is there really a heavy need to support the giant fbx file format as native format?

PS2: Just have a look at other engines.. e.g. CryTek..