Yeah it would be a great to have in your game, but for most of us smaller dev teams (like my team: just me 
) it is quite a task to implement that functionality.
Using FBX would probably be the easiest file format to get all of the textures and normal maps included and showing up correctly on the mesh all in one file, but I suppose it is possible to base your custom importer off of a different file format as well such as OBJ etc. But who knows, may even make things more complex to implement, so no matter what there doesn’t seem to be any shortcuts currently without the engine licencing.
Would be interested to hear if anyone has done in UE4 though!